U. S. DEPARTMENT OF THE INTERIOR 

U. S. GEOLOGICAL SURVEY

40Ar/39Ar Age-Spectrum Data for Amphibole, Muscovite, Biotite, and K-feldspar samples from 

metamorphic rocks in the Blue Ridge Anticlinorium, northern Virginia

by

Michael J. Kunk 

U.S. Geological Survey, MS 974, Denver, Colorado 80225

and

William C. Burton 

U.S. Geological Survey, MS 926A, Reston, Virginia 22092

Open-File Report 99-552 

1999

This report is preliminary and has not been edited or reviewed for conformity with U.S. Geological

Survey editorial standards or with the North American Stratigraphic Code. Any use of trade, 

product or firm names is for descriptive purposes only and does not imply endorsement by the U.S

Government.
TABLE OF CONTENTS

INTRODUCTION 3

METHODS 3

Sample Preparation 3

Sample Analysis 3

Isotopic Data Reduction 4

SAMPLE LOCATIONS 6

RESULTS 7

40Ar/39Ar Data 7

Condensed Tabular Argon Data 9

40Ar/39Ar Data Tables 11

REFERENCES 110
INTRODUCTION

The Blue Ridge tectonic province in 

northern Virginia consists of a Middle 

Proterozoic basement core of granites and 

gneisses that are unconformably overlain by a 

cover sequence of Late Proterozoic and Early 

Paleozoic metavolcanic and metasedimentary 

rocks. This area has been the subject of 

detailed geological mapping (McDowell and 

Milton, 1992; Burton, et al., 1995; 

Southworth, 1994; 1995; and Southworth and 

Brezinski,1996) that has raised questions 

about the timing and intensity of Paleozoic 

metamorphism in this part of the Blue Ridge.

This publication contains reduced 

40Ar/39Ar data of hornblende, phlogopite, 

muscovite, biotite, and K-feldspar mineral 

separates from metamorphic rocks of Blue 

Ridge anticlinorium in northern Virginia. 

This data will be used to answer some of the 

questions regarding the timing and intensity

of Paleozoic metamorphism in the Blue Ridge 

of northern Virginia, and is intended only to 

be a preliminary publication of these results, 

in more detail than can be accommodated in 

today's professional journals. Also included 

in this report is information on the location of 

the samples, and the formation or lithology 

from which the sample was collected. The 

data contained herein are not interpreted in a 

geological context, and care should be taken 

by users unfamiliar with argon isotopic data 

in the use of these results. No geological 

meaning is implied for any of the apparent 

ages presented below and many of the 

individual apparent ages are not geologically 

meaningful. This report is primarily a detailed 

source document for subsequent publications 

that will integrate these data into a geological 

context.

METHODS

Sample Preparation

All of the samples were crushed, 

ground, and sized using 250, 180, and 150 

|im sieves. Mineral separates were produced 

using magnetic separation, heavy liquid 

separation, paper shaking, and hand picking 

to a purity >99% for muscovite, biotite, and 

Kspar and >99.9% for hornblende. The 

samples were washed in acetone, alcohol, and 

deionized water(X3) in a Branson B-220 

ultrasonic cleaner to remove dust and then resieved by hand using a 100 \im sieve. 

Approximately 100 mg of hornblende and 10 

mg of muscovite, biotite, and Kspar were 

packaged in aluminum capsules and sealed 

under vacuum in quartz tubes. The type of 

container, and the geometry of samples and 

standards is similar to that described by Snee 

et al. (1988). The samples were irradiated in 

six separate packages (RD72, RD74 RD77,

RD80, RD87, and RD93) in the central 

thimble facility at the TRIGA reactor (GSTR) 

at the U.S. Geological Survey, Denver, 

Colorado. The monitor mineral used in all 

packages was MMhb-1 with an age of 519.4 

± 2.5 Ma (Alexander et al.,1978; and 

Dalrymple et al., 1981).

Sample Analysis

All samples were analyzed on a VG 

Isotopes, Ltd, Model 1200 B Mass 

Spectrometer fitted with a Faraday cup 

collector at the U.S. Geological Survey, 

Reston, VA using the 40Ar/39Ar step heating 

method of dating. Heating for 15 minutes 

(RD72, RD74 RD77, RD80& RD87) or 10 

minutes (RD93) per step followed a schedule 

of 1-22 steps per sample. For most 

samples,the number and temperature of 

heating steps was selected to limit the
percentage of gas released to less than 5- 

20%/step for most samples. Most biotite 

samples were totally fused.

Heating of samples was done in a 

small volume, molybdneum-lined low blank 

tantalum furnace similar to that described by 

Staudacher (1978). Temperature was 

monitored by a W5Re-W26Re thermocouple 

and controlled by a proportional, 

programmable controller.

The furnace and the rear manifold 

were pumped between steps with a turbo 

molecular pump. Two isolated ion pumps 

evacuated the front manifold and the mass 

spectrometer tube between each incremental 

step.

The gas to be analyzed was purified 

in the rear manifold by a SAES ST707 Zr-VFe getter operated at room temperature and a 

hot filament. Gas was equilibrated with the 

front manifold with an empty cold finger in 

the first manifold at LNi temperature to trap 

water, then isolated and cleaned in the front 

manifold with a SAES ST101 Al-Zr getter 

operated at 400° C and a Ti getter operated at 

350° C.

For all samples, an activated charcoal 

finger submerged in a constant boiling 

mixture of dry ice and acetone was used to 

remove gasses with a molecular weight 

greater than 60 or 80 (primarily other noble 

gasses) prior to the admission of the argon 

dominated gas to the mass spectrometer by 

expansion. The argon-rich gas was further 

purified in the mass spectrometer by a second 

SAES ST101 active gas getter operated at 

room temperature. Its successful operation 

could be monitored by the drop in counts of 

mass 44 (dominated by CO2) after the first 

gas analysis cycle. Argon isotopes with 

masses 40 through 36 and CO2, mass 44 were 

analyzed as a function of time in five analysis 

cycles. 40Ar, 39Ar, 38Ar, 37Ar and 36Ar peaks 

and their baselines, were measured for five 

second integrations in each of the five cycles 

with a faraday cup collector. After the

analysis the mass spectrometer was evacuated 

All phases of the sample heating, cleanup, 

equilibration and sample analysis were 

preformed under computer control.

Isotopic Data Reduction

All the Ar isotopic data were reduced 

using an updated version of the computer 

program ArAr* (Haugerud and Kunk, 1988) 

and decay constants recommended by Steiger 

and Jager (1977). The isotopic measurements, 

made in the five-cycle analysis, had baseline 

values subtracted and then were regressed to 

time zero, using standard linear regression 

techniques. These regressed values and 

associated statistical estimates of analytical 

uncertainties of the time zero peak values 

were used in the data reduction. For our 

samples the system blank in all cases was 

atmospheric in composition, was less than 

0.1 %of the signal, and was not subtracted. 

Corrections for interfering reactor-produced 

argon isotopes from Ca, K, and Cl in the 

sample were made using the production ratios 

given in Dalrymple et al. (1981) and 

Roddick(1983). Errors in calculating ages or 

ratios include: analytical errors in the 

analysis; decay factor uncertainties; measured 

atmospheric or calculated initial 40Ar/36Ar 

ratios; the irradiation parameter J; the 

production ratios of the various reactor 

induced argon producing reactions; the initial 

38Ar/36Ar ratio; and the uncertainty in the age 

of the monitor mineral (Haugerud and Kunk, 

1988).

The tables and figures below include 

the identification of individual step ages, 

Minimum ages, maximum ages, plateau ages, 

and total gas ages. We have used the plateau 

test of Fleck, Sutter and Elliot (1977), as 

modified by Haugerud and Kunk (1988) to 

determine if an age spectrum has an age 

plateau. Total gas ages represent the age 

calculated from the addition of all of the 

measured argon peaks for all steps in a single
sample. The total gas ages are roughly 

equivalent to conventional K/Ar ages. No 

analytical precision is calculated for total gas 

ages in an age spectrum. Isotope correlation 

analysis of the analytical data to assess if nonatmospheric argon components were trapped 

in any samples and to calculate an isochron 

age was also preformed and the results are 

presented.
SAMPLE LOCATIONS

Table A. Location of the samples included in this report from the Blue Ridge of northern Virginia. 

The mineral analyzed and unit from which the sample collected are indicated.

Sample #

HF2-90 

Kline 

PulA 

RRNB-400 

YNPVILLE

LN-186

K92-7-15B

BR138

BR873

BR904

CBR- 10-92

T185B

T65

K92-7-11A

K92-7-11B

K92-7-11C

K92-7-29A

CBR- 10-92

RR89-28

K92-5-16B

K92-5-17B

K92-5-17C

K92-8-4B

K92-8-4D

CBR- 10-92

RRNB-400

RR89-28

K92-5-16A

K92-5-16B

K92-5-17C

Mineral

Hornblende 

Hornblende 

Hornblende 

Hornblende 

Hornblende

Phlogopite

Phlogopite

Muscovite

Muscovite

Muscovite

Muscovite

Muscovite

Muscovite

Muscovite

Muscovite

Muscovite

Muscovite

Biotite

Biotite

Biotite

Biotite

Biotite

Biotite

Biotite

Kspar

Kspar

Kspar

Kspar

Kspar

Kspar

N 

Latitude

39° 

38° 

39° 

38° 

39°

39°

39°

39°

39°

39°

37°

39°

39°

38°

38°

38°

39°

37°

38°

38°

38°

38°

38°

38°

37°

38°

38°

39°

38°

38°

17' 

59' 

13' 

45' 

13'

02'

or

16'

16'

16'

47'

41'

42'

49'

49'

49'

17'

47'

29'

52'

54'

54'

35'

38'

47'

45'

29'

07'

52'

54'

W 

Longitude

14" 77° 

35" 77° 

58" 77° 

56" 78° 

57" 77°

01"

28"

47"

12"

13"

52"

28"

23"

30"

30"

33"

06"

52"

50"

46"

50"

50"

07"

25"

52"

56"

50"

08"

46"

50"

77°

77°

77°

77°

77°

78°

77°

77°

77°

77°

77°

77°

78°

78°

77°

77°

77°

77°

77°

78°

44' 

43' 

44'

or

41'

40'

40'

44'

33'

32'

45'

51'

51'

42'

42'

42'

44'

45'

12'

51'

46'

46'

57'

54'

45'

78° 01

78°

77°

77°

77°

12'

47'

51'

46'

24" 

23" 

58" 

35" 

13"

46"

50"

20"

15"

41"

40"

43"

40"

34"

34"

47"

20"

40"

06"

32"

25"

25"

03"

57"

40"

'35"

06"

30"

32"

25"

7 1/2' Quadrangle

Harpers Ferry VA-MD-WV 

Middleburg VA 

Purcellville VA 

Flint Hill VA 

Purcellville VA

Lincoln VA

Lincoln VA

Point of Rocks MD-V A

Point of Rocks MD-V A

Point of Rocks MD-VA

Lovingston VA

Thoroughfare Gap VA

Thoroughfare Gap VA

Thoroughfare Gap VA

Thoroughfare Gap VA

Thoroughfare Gap VA

Harpers Ferry VA-MD-WV

Lovingston VA

Brightwood VA

Rectortown VA

Rectortown VA

Rectortown VA

Brandy Station VA

Jeffersonton V A

Lovingston VA

Flint Hill VA

Brightwood VA

Bluemont VA

Rectortown VA

Rectortown VA

Unit

Quartz Monzonite 

Metagabbro 

Charnockite 

Laurel Mills Granite 

Mt Zion Norite

Catoctin Formation

Catoctin Formation

Catoctin Formation

Weaverton Formation

Loudoun Formation

Lynchburg Formation

Weaverton Formation

Weaverton Formation

Weaverton Formation

Weaverton Formation

Weaverton Formation

Swift Run Formation

Lynchburg Formation

Laurel Mills Granite

Marshall Granite

Marshall granite

Marshall granite

Lynchburg Formation

Ball Mtn. Formation

Lynchburg Formation

Laurel Mills Granite

Laurel Mills Granite

Marshall Granite

Marshall Granite

Marshall Granite
RESULTS

40Ar/39Ar Data

The 40Ar/39Ar data presented in this 

report are presented in two different formats. 

Data within both formats are arranged in the 

same order as the section on sample locations 

(Table A.). The first of these formats is a 

condensed tabular form (Table B). The data 

presented in this table are organized by the 

mineral analyzed. These tables summarize the 

data contained in the succeeding, more 

detailed individual data sets. Included in this 

table are: the sample numbers; the material 

analyzed; the apparent age and its error (see 

below for a detailed explanation); the percent 

39Ar of the total that this apparent age 

represents; the number of steps / total number 

of steps that this apparent age represents; and; 

a comment listing the type of apparent age. 

For inverse isotope correlation ages, the table 

includes the MS WD (a goodness of fit 

indicator) and the calculated initial 40Ar/36Ar 

ratio.

The individual data sets include a 

series of four tables, as well as one or two 

graphical representations of some of the age 

spectrum data. The tables are numbered nA, 

nB, nC, and nD, and the figures share the 

same number, n, for a given sample. No 

figures are presented for biotite samples that 

were totally fused.

The first table, RAW DATA, includes 

the computer file number of the individual 

argon analysis, the temperature of the step, 

regressed peak values and their precision, the 

trap current (filament amperage, in 

microamps) and the manifold splitting option 

used. The relationship between the trap 

currents and manifold options can be found in 

the footnotes of the third table. No corrections 

have been made to the peak values, these are

raw numbers. Included as table footnotes are: 

(1) the measured atmospheric 40Ar/36Ar ratio 

for calculation of mass spectrometer 

discrimination; (2) the trap current at which 

the samples were run in micro amps of 

current; ( 3) the manifold splitting option 

used; (4) the sensitivity of the mass 

spectrometer at the time of the analysis; (5) 

an estimate of the limit of reproducibility of 

the mass spectrometer when the sample was 

analyzed (If an intra-sample error is less than 

this value times the age of the step, this value 

should be used when comparing with other 

steps from the same age spectrum) and; the 

detection limit of the mass spectrometer in 

counts. For a further explanation of these 

footnotes see Haugarud and Kunk, 1988. 

The second table, CORRECTIONS, contains 

calculated corrections for decay of 

radioactive isotopes of argon, as well as the 

production of interfering isotopes during 

irradiation, and a calculated initial 38Ar value. 

All of these values have been corrected only 

for the affects of mass discrimination as 

discerned by measuring atmospheric argon. 

All tabular data in this table, as well as the 

two subsequent tables, is indexed by the 

temperature of the step analyzed.

The third data table, MOLAR 

VALUES, lists molar quantities of the 

indicated argon isotope derived from the 

sources indicated. The age of the step and an 

estimate of intra-sample precision in millions 

of years (Ma) are given. All precision 

estimates, in all tables, are at the one sigma 

level of confidence. The precision stated for 

the ages of individual temperature steps does 

not include the error in J.

The fourth table includes the percent 

of potassium derived 39Aric of the age 

spectrum total that each step contains, the
radiogenic yield (percentage of 40Ar (R) that 

is derived from the decay of potassium), 

calculated apparent K/Ca and K/C1 ratios for 

each step (or asterisk if the measured 38Ar or 

37Ar signal measured was less than the 

detection limit of the mass spectrometer), a 

corrected 40ArR/39ArK ratio from which the 

age can be directly calculated, a calculated 

age for the step, in millions of years and an 

estimate of the precision of each age. The 

sample precision includes estimates of the 

errors that are unique to a single sample and 

can be used only for comparisons with other 

steps of the same sample. This error estimate 

does not include the error in "J", except for 

total fusion analyses. The J-value and its 

precision estimate, and sample weight are 

listed near the top of this table. 

One or two figures are included with each age 

spectrum data set. The first figure includes 

one or two graphs. The lower and larger 

graph plots cumulative percent 39ArK of the 

steps in the age spectrum against apparent age 

in millions of years. The precision estimate 

used to construct the error boxes of each step 

is two sigma. The upper, smaller graph plots 

the apparent K/Ca ratio of each step against 

cumulative 39ArK released. Many times the 

degree of sample purity or the presence of 

compositional zoning can be inferred from 

this figure. Homogeneous samples with no 

compositional zoning or impurities are 

reflected by horizontal patterns in this figure, 

the patterns of those with zoning or impurities 

typically depart from horizontal.

The second figure is an inverse 

isotope correlation diagram, and plots 

39Ar/40Ar vs 36Ar/40Ar for each of the steps of 

the age spectrum data. In many cases the data 

is linearly regressed by the method of York 

(1969). For this graph to have any meaning, 

the regressed line must have a negative slope. 

The X-axis intercept is the inverse of the

40 /39 Ar/ Ar ratio and can be used to calculate an 

age for the sample. The Y-axis intercept is the

for the sample. This ratio should have a value 

of 295.5 (modern atmosphere) or greater if 

the isotope correlation data is to be 

considered useful. Included in the caption of 

these figures is the MSWD of the points used 

in the isochron. The MSWD is a goodness of 

fit indicator and a value of 2.5 or less 

indicates a good fit of the data to the line. 

For additional information on the sample data 

sets see Haugerud and Kunk(1988).

40 /36 inverse of the calculated initial Ar/ Ar ratio
Table B. Summary of argon isotopic results from the Blue Ridge of northern Virginia.

Sample #

HF2-90

Kline

PulA

RKNB-400

YNPVILLE

LN-186

K92-7-15B

BR138

BR873

BR904

CBR- 10-92

T185B

T65

K92-7-1 1 A

K92-7-11B

K92-7-11C

K92-7-29A

CBR-10-92

RR89-28

K92-5-16B

K92-5-17B

K92-5-17C

K92-8-4B

Mineral

Hornblende

Hornblende

Hornblende

Hornblende

Hornblende

Phlogopite

Phlogopite

Muscovite

Muscovite

Muscovite

Muscovite

Muscovite

Muscovite

Muscovite

Muscovite

Muscovite

Muscovite

Biotite

Biotite

Biotite

Biotite

Biotite

Biotite

Apparent 

Age (Ma)

978 ±2

956.6 ±22.5

1000.4 ±4.3

992.9 ± 4.2

997.76

920 ±2

919.7 ±3.0

548.3

523.9 ±2.4

1022

1008 ±5.4

405.7 ±2.0

404.7 ± 2.3

409

403.8 ± 4.7

313

338

323

347

311

360

338

346

297

337

316

333

318

334

135

214

325

334

337

347

340 ±1.56

337.7 ±1.7

337.7 ±2.3

329 ± 1.53

396 ±1.80

383 ±1.76

370 ±1.70

%Jt)Ar

84.3

96.6

55.7

67.0

13.8

13.8

100

100

100

15.4

72.7

74.7

100

6.2

62.0

7.5

7.5

4.2

12.0

6.5

1.6

8.0

8.1

3.3

10.7

3.5

5.7

3.1

9.0

28.2

5.8

3.3

10.1

6.0

6.1

100

70.2

91.3

100

100

100

100

Steps 

Total

6/11

8/11

2/7

5/7

1/7

6/9

9/9

16/16

16/16

1/7

4/7

6/11

11/11

1/12

8/12

1/8

1/8

1/9

1/9

1/9

1/9

1/7

1/7

1/9

1/9

1/10

1/10

1/8

1/8

1/6

1/6

1/8

1/8

1/7

1/7

1/1

6/11

8/11

1/1

1/1

1/1

1/1

Initial 4UAr/36Ar

295.5

3830 ±2764

295.5

821 ±20

295.5

295.5

-1504 ±22

295.5

492 ±3

295.5

1527 ±140

295.5

396 ± 85

295.5

460 ± 59

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

274 ± 63

295.5

295.5

295.5

295.5

MSWD Comment

Preferred age

Isochron

Plateau age

1.58 Isochron

Minimum

Preferred

5.04 Isochron

Total Gas

473 Isochron

Minimum

1.015 Isochron

Plateau

0.803 Isochron

Minimum

1.151 Isochron

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Total Gas

Plateau

0.328 Isochron

Total Gas

Total Gas

Total Gas

Total Gas
Table B (Cont.). Summary of argon isotopic results from the Blue Ridge of northern Virginia.

Sample #

K92-8-4D

CBR- 10-92

RRNB-400

RR89-28

K92-5-16A

K92-5-16B

K92-5-17C

Mineral

Biotite

Kspar

Kspar

Kspar

Kspar

Kspar

Kspar

Apparent %39Ar 

Age (Ma)

377 ±1.71

202

698

213

335

183

349

228

457

223

534

184

577

100

8.8

7.8

2.5

6.1

4.9

4.4

4.8

13.5

4.2

9.4

9.2

2.2

Steps Initial 4UAr/36Ar MSWD Comment 

Total

1/1

1/17

1/17

1/22

1/22

1/18

1/18

1/12

1/12

1/15

1/15

1/16

1/16

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

295.5

Total Gas

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

10
Table 1A. HF-2-90 HORNBLENDE #23RD80 v 4/17/98 08:28:16 15 Sep 1999

RAW DATA

File#

31177

31178

31179

31180

31181

31182

31183

31184

31185

31186

31187

All values are

Precisions are

Temperature

950

±

1000

±

1020

±

1040

±

1050

±

1060

±

1080

±

1100

±

1125

±

1150

±

1175

±

40Ar

1321497

2785

2307845

2323

1514551

2606

1653850

236

4264587

6489

5041670

11429

2597050

5987

2952407

5649

4491956

7857

2906753

1906

1147649

2214

in counts. Measured 40Ar/36Ar

39Ar

24454

34

34995

35

20374

68

21860

40

56135

129

66204

130

34362

39

38230

80

59197

88

37642

84

14800

24

= 290.8 ± 0.

38Ar

2111

14

5919

10

3985

18

4290

32

11543

37

13667

35

6987

24

7877

40

12136

24

7756

40

3020

24

.2

37Ar

187

8

558

20

257

11

250

20

484

24

615

10

435

11

332

4

715

9

406

11

140

15

36Ar

166

2

124

4

39

5

34

2

88

2

94

1

44

3

52

3

66

2

54

1

32

3

Trap current

200

200

200

100

100

100

100

100

100

100

100

Manifold

BALL

BALL

ESPLIT

ESPLIT

EALL

EALL

ESPLIT

EALL

ESPLIT

ESPLIT

EALL

1

1

2

2

1

at the 1 sigma level and are from linear regression statistics.

Trap current factors: 40 = 5.66

Manifold factors: All = 1

Sensitivity =

EA11 = 2

100-2.62 200- 1

Splitl - 3.3 Split2 = 10.89

Esplitl = 6.6 Esplit2 =

1.647 X10" 17 moles/count. Reproducibility

21.78

limit = .25 %. Detection limit = 40 counts.

11
Table IB. HF-2-90 HORNBLENDE #23RD80 v 4/17/98 08:28:16 15 Sep 1999

CORRECTIONS

Temp 39Ar 37Ar - K-derived Ca-derivec 

(°C) decay decay 40Ar 38Ar 37Ar 39Ar

950 48 41563 138 327 0 28

1000 69 124360 198 467 0 83

1020 40 57239 115 272 0 38

1040 43 55637 124 292 0 37

1050 111 108091 318 750 0 72

1060 131 137327 375 884 0 92

1080 68 97154 194 459 0 65

1100 75 74143 216 511 0 50

1125 117 159989 335 790 0 107

1150 74 90970 213 503 0 61

1175 29 31457 84 198 0 21

38Ar 36Ar

1 11

4 33

2 15

2 15

3 28

4 36

3 25

2 19

5 42

3 24

1 8

Cl-derived initial

36Ar 38Ar

1 28

3 16

2 4

2 3

6 10

7 9

3 3

4 5

6 3

4 5

1 4

All values are in counts and have been corrected for mass discrimination.

Table 1C. HF-2-90 HORNBLENDE #23RD80 v 4/17/98 08:28:16 15 Sep 1999

MOLAR VALUES

Temperture 40Ar* 39ArK 38Arc, 37Ca

(°C)

950 4.352554 0.080299 0.005913 0.135884

1000 7.601391 0.114769 0.017850 0.406571

1020 16.462215 0.220610 0.040045 0.617535

1040 47.097996 0.620266 0.112968 1.572648

1050 36.801837 0.482861 0.092428 0.925861

1060 43.507787 0.569417 0.109447 1.176274

1080 244.062192 3.216924 0.608426 9.062342

1100 25.478234 0.328841 0.063074 0.635068

1125 422.139353 5.542359 1.057246 14.923410

1150 82.778045 1.068150 0.204907 2.571353

1175 9.903809 0.127289 0.024179 0.269443

All gas quantities are in moles x 10" 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

36ATi

0.000498

0.000286

0.000229

0.000479

0.000451

0.000430

0.001359

0.000242

0.001591

0.000731

0.000186

Apparent Age

(Ma)

727.36

871.45

962.18

976.07

978.42

980.85

976.46

991.52

979.82

991.84

992.62

Precision

(Ma)

1.34

0.82

1.51

0.36

1.17

1.72

1.77

1.48

1.33

0.52

1.60

12
Table ID. HF-2-90 HORNBLENDE #23RD80 v 4/17/98 08:28:16 15 Sep 1999

Temperature % 39Ar 

°C of total

J - 0.009482 ±

950

1000

1020

1040

1050

1060

1080

1100

1125

1150

1175

Total Gas

NO PLATEAU

0.5%

0.6

0.9

1.8

5.0

3.9

4.6

26.0

2.7

44.8

8.6

1.0

100.0

Radiogenic 

Yield (%)

39 A r ATK 40Ar*/39ArK Apparent 

K/Ca

Apparent 

K/C1

Apparent Age Precision 

Ma Ma

Sample wt. - 0.3300g

96.6

98.9

99.6

99.7

99.6

99.7

99.8

99.7

99.9

99.7

99.4

99.8

0.080299

0.114769

0.220610

0.620266

0.482861

0.569417

3.216924

0.328841

5.542359

1.068150

0.127289

12.371785

52.373

65.496

74.314

75.704

75.940

76.185

75.743

77.262

76.081

77.294

77.373

75.840

0.31

0.15

0.19

0.21

0.27

0.25

0.18

0.27

0.19

0.22

0.25

0.20

33

16

13

13

13

13

13

13

13

13

13

13

727.36

871.45

962.18

976.07

978.42

980.85

976.46

991.52

979.82

991.84

992.62

977.42

±

±

±

±

±

±

±

±

±

±

±

1.34

0.82

1.51

0.36

1.17

1.72

1.77

1.48

1.33

0.52

1.60

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

13
Figure 1A. Age spectrum for HF-2-90 hornblende. 

1 r 

O

.1

1000

900

=

OH 

"

800

700

n

J=f=t

0

HF-2-90 

HORNBLENDE

I I I I

39An, RELEASED (%) N. v /

100

14
Figure IB. Inverse isotope correlation diagram for HF-2-90 hornblende. Points D,E,F,G,H,I,J, and 

K, which contain 96.6% of the 39Ar released, were regressed. MSWD = 0.626, SUMS = 3.756, 

initial 40Ar/36Ar = 3830 ± 2764, and apparent age = 956.6 ± 22.5 Ma.

(N

O 

O 

O

<0 

00

<o 

W 

rf

HF-2-90

B

.003 .006 .009 .012 .015 .018

39\ /40A Ar/ Ar

W/O POINTS ABC

15
Table 2A. Kline Hornblende #54,55&56 RD74 v. 4/17/98 9:47:13 AM 9/14/1999

RAW DATA

File# Temperature 40Ar 39Ar 38Ar

25404 1150 1691040 15737 1813

± 1624 27 9

25405 1200 2523726 27208 2647

± 1568 22 13

25406 1200 3735906 41067 3873

± 1919 34 15

25407 1250 2020016 22306 2078

± 806 25 7

25408 1250 3994358 44268 4099

± 1555 29 19

25409 1350 1906889 20854 1983

± 1892 2 9

25410 1350 2916707 30943 3011

± 1460 32 1

All values are in counts. Measured 40Ar/36Ar = 296.5 ±0.5

37Ar

25028

28

38361

24

57520

33

30950

31

61467

29

28606

10

43039

10

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 3.57 100 = 2.15 200 = 1 

Manifold factors: All - 1 Splitl - 4.2 Split2 = 10.89 

EAI1 = 2 Esplitl - 6.6 Esplit2 - 21.78 

Sensitivity = 2.15 X 10" 17 moles/count. Reproducibility limit = .25 %. Detection

36Ar

376

7

148

2

166

9

56

3

143

5

45

6

242

12

limit =

Trap current

200

200

40

40

40

40

100

40 counts.

Manifold

ALL

SPLIT 1

ALL

SPLIT 1

ALL

SPLIT 1

ALL

Table 2B. Kline Hornblende #54,55&56 RD74 v. 4/17/98 9:47:13 AM 9/14/1999

CORRECTIONS

Temp 39Ar 37Ar - K-derived 

(°C) decay decay 40Ar 38Ar 37Ar 39Ar

1150 7 63206 89 210 0 60

1200 12 96977 154 364 0 91

1200 19 145543 233 549 0 137

1250 10 78397 126 298 0 74

1250 20 155832 251 592 0 147

1350 10 72597 118 279 0 68

1350 14 109325 175 414 0 103

All values are in counts and have been corrected for mass discrimination.

Ca-derivec

38Ar

3

4

6

3

7

3

5

36Ar

23

36

54

29

58

27

40

Cl-derived initial 

36Ar 38Ar

0 66

0 21

0 21

0 5

0 16

0 3

0 38

16
Table 2C. Kline Hornblende #54,55&56 RD74 v. 4/17/98 9:47:13 AM 9/14/1999

MOLAR VALUES

Temperture 40Ar* 39ArK 38Arc, "Ca 36Ar; 

(°C)

1150 36.355448 0.337498 0.035883 1.901847 0.007602 

1200 227.878554 2.451876 0.208128 12.252099 0.010187 

1200 286.731588 3.145715 0.256739 15.625602 0.008647 

1250 651.153946 7.176480 0.575418 35.339732 0.008589 

1250 306.567668 3.390997 0.270399 16.721115 0.006586 

1350 614.687623 6.709412 0.550685 32.707865 0.005896 

1350 134.816653 1.427470 0.121833 7.060882 0.009341

Apparent Age 

(Ma)

1091.12 ± 

1013.73 ± 

1002.06 ± 

1002.43 ± 

997.76 ± 

1010.71 ± 

1020.47 ±

Precision 

OVIa)

1.31 

0.52 

0.66 

0.50 

0.43 

1.04 

1.01

All gas quantities are in moles x 10 l2 . 

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0. 

All precision estimates are at the one sigma level of precision. 

Ages of individual steps do not include error in the irradiation parameter J. 

No error is calculated for the total gas age.

Table 2D. Kline Hornblende #54,55&56 RD74 v. 4/17/98 9:47:13 AM 9/14/1999

Temperature % 39Ar Radiogenic 39ArK 40Ar*/39ArK Apparent Apparent 

°C of total Yield (%) K/Ca K/C1

1=0.008222 ± 0.50% Sample wt. - 0.9019 

1150 1.4 93.8 0.337498 101.064 0.09 23 

1200 10.0 98.7 2.451876 91.713 0.1 29 

1200 12.8 99.1 3.145715 90.338 0.1 30 

1250 29.1 99.6 7.176480 90.381 0.11 30 

1250 13.8 99.4 3.390997 89.832 0.11 30 

1350 27.2 99.7 6.709412 91.356 0.11 29 

1350 5.8 98.0 1.427470 92.511 0.11 28 

Total Gas 100.0 99.3 24.639448 90.968 0.105 29.573

55.66% of qas on plateau in 1200 through 1250 steps Plateau Age =1000.36 ±

Apparent Age 

Ma

g 

1091.12 ± 

1013.73 ± 

1002.06 ± 

1002.43 ± 

997.76 ± 

1010.71 ± 

1020.47 ± 

1007.42

4.29

Precision 

Ma

1.31 

0.52 

0.66 

0.50 

0.43 

1.04 

1.01

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0. 

All precision estimates are at the one sigma level. 

Ages of individual steps do not include error in the irradiation parameter J. 

No error is calculated for the total gas age. 

39ArK gas quantities are in moles x 10~' 2 .

17
Figure 2A. Age spectrum for KLINE hornblende.

1 E

a

.1

.01

Jp 1000

o.

900

0

KLINE 

HORNBLENDE

I I I

39ArK RELEASED (%)

Iv x /

100

18
Figure 2B. Inverse isotope correlation diagram for KLINE hornblende. Points A,B,C,D, and E, 

which contain 67.0% of the 39Ar released, were regressed. MSWD = 1.577, SUMS = 4.731, initial 

40Ar/36Ar = 821.3 ± 20.1, and apparent age = 992.9± 4.2 Ma.

o 

o 

o

vO-« 

m o 

o 

o

KLINE

.002 .004 .006

AT/ Ar

.008 .01 .012

W/O POINTS FG

19
Table 3A.PU-1 A Hornblende #36,37&38 RD72 v. 4/17/98 9/14/1999 11 :19:14 AM

RAW DATA

File# Temperature 40Ar 39Ar 38Ar 37Ar

26325 1050 3979994 91892 6311 2320

± 1913 83 40 9

26326 1100 2097807 33130 983 1353

± 903 18 13 8

26327 1100 1444845 21999 514 948

± 222 15 9 8

26328 1150 2795016 41943 878 1841

± 428 19 9 10

26329 1175 2649519 39614 836 1713

± 1330 22 13 6

26330 1200 1360905 20414 423 883

± 210 18 11 9

26331 1225 4890412 72964 1481 3195

± 944 27 13 13

26332 1250 1519146 22821 463 970

± 496 9 11 12

26333 1250 3918942 58588 1159 2708

± 2658 56 23 12

All values are in counts. Measured 40Ar/36Ar = 297.2 ± 0.5

Precisions are at the 1 sigma level and are from linear regression statistics.

Trap current factors: 40 = 3.57 100 = 1.4 200 = 1

Manifold factors: All - 1 Split 1 = 4.2 Split2 = 17.64

EAII = 2 Esplitl = 6.6 Esplit2 = 21 .78 

Sensitivity = 1.344 X " l7 moles/count. Reproducibility limit = .25 %. Detection

36Ar

1465

15

50

3

32

6

52

5

45

3

23

3

64

3

27

7

67

5

Trap current Manifold

200 ALL

200 SPLIT

200 SPLIT

200 SPLIT

200 SPLIT

200 SPLIT

200 SPLIT

200 SPLIT

200 ALL

2

3

2

2

2

1

2

limit = 40 counts.

Table 3B.PU-1 A Hornblende #36,37&38RD72 v. 4/17/98 9/14/1999 11

CORRECTIONS

Tptnn 39Ar 37 Ar k' HprivpH ,. - f i Hprivpr 1 ciiip ^" m ~ ~ rv-uciivcu - _____ v^a-uciivci -_ 

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar

1050 137 133026 523 1234 0 91 4

1100 49 77653 188 445 0 53 3

1100 33 54459 125 295 0 37 2

1150 62 105836 239 563 0 73 3

1175 59 98537 225 531 0 68 3

1200 30 50844 116 274 0 35 2

1225 109 184100 415 979 0 127 6

1250 34 55930 130 306 0 38 2

1250 87 156277 333 786 0 107 5

All values are in counts and have been corrected for mass discrimination.

36

21

15

29

27

14

50

15

42

:19:14AM

Cl-derivec initial

36Ar 38Ar

2 268

0 5

0 3

0 4

0 4

0 2

0 3

0 2

0 5

20
Table 3C. PU-1A Hornblende #36,37&38 RD72 v. 4/17/98 9/14/1999 11:19:14 AM

MOLAR VALUES

Temperture 40Ar* 39ArK 38Arc , "Ca 

(°C)

36Ari Apparent Age 

(Ma)

J = 0.009991 ± 0.25% Sample wt. =

1050 53.484092 1.237415 0.072043 1.826896 0

1100 497.306745 7.864962 0.129015 18.811640 0

1100 1534.722356 23.398486 0.235874 59.112621 0

1150 662.590332 9.955850 0.075617 25.638328 0

1175 628.098848 9.403120 0.072766 23.869888 0

1200 322.618009 4.845700 0.035631 12.316413 0

1225 276.030544 4.123616 0.028395 10.618039 0

1250 360.130751 5.417122 0.037535 13.548051 0

1250 52.666104 0.788289 0.005059 2.145970 0

All gas quantities are in moles x 10~' 2 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

.019295

.006893

.018010

.005601

.004513

.002129

.000807

.002727

.000337

1.0029g

588.61

880.46

906.72

917.85

920.75

918.52

923.20

917.25

921.07

±

±

±

±

±

±

±

±

±

Precision 

(Ma)

0.68

0.44

0.83

0.42

0.44

0.42

0.21

1.05

0.56

Table 3D. PU-1A Hornblende #36,37&38 RD72 v. 4/17/98 9/14/1999 1 1:19:14 AM

Temperature % 39Ar Radiogenic 39ArK 40Ar*/39ArK Apparent

°C of total Yield (%) K/Ca

1 = 0.009991 ±0.25%

1050 1.8 89.3 1.237415 38.615 0.35

1100 11.7 99.6 7.864962 62.972 0.22

1100 34.9 99.7 23.398486 65.363 0.21

1150 14.9 99.8 9.955850 66.387 0.20

1175 14.0 99.8 9.403120 66.655 0.20

1200 7.2 99.8 4.845700 66.448 0.20

1225 6.2 99.9 4.123616 66.881 0.20

1250 8.1 99.8 5.417122 66.331 0.21

1250 1.2 99.8 0.788289 66.684 0.19

Total Gas 100.0 99.5 0.000000 65.188 0.21

NO PLATEAU

Ages calculated assuming an initial 40Ar/36Ar = 295.5 ± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10" 12 .

Apparent Apparent Age

K/C1

Sample

42

148

240

319

313

329

351

349

377

271

Ma

Precision

Ma

wt= 1.0029 g

588.61

880.46

906.72

917.85

920.75

918.52

923.20

917.25

921.07

904.81

±

±

±

±

±

±

±

±

±

0.68

0.44

0.83

0.42

0.44

0.42

0.21

1.05

0.56

21
Apparent Age (Ma) K/Ca

to 

to

^

c 

c

o

Jrt

r

w

w

o^-N

^0^

* ^

0

n o\ ^ oo \O O ^ooooo- 

^ooooo 

u l 1 1 1

r

o

w

1

o
Figure 3B. Inverse isotope correlation diagram for Pu-lA hornblende. Regressing all points. 

MSWD = 5.04, SUMS = 35.3, initial 40Ar/36Ar = -1504± 21.6, and apparent age - 919.7± 3.0 Ma. 

Deletion of points from the regression did not improve the results.

m O 

o

O

O 

O

o

o 

o 

o

PU-IA

.004 .008 .012 .016

39AiAr

.02 .024

23
Table 4A. RRNB-40Q HORNBLENDE #57,58&59 RD74 v.9/21/99 14:34:58 16 Sep 1999

RAW DATA

All

File#

26532

26533

26534

26535

26536

26537

26538

26539

26541

26542

26543

26544

26545

26546

26547

26548

values are

Temperature

850

±

1000

±

1050

±

1075

±

1100

±

1125

±

1125

±

1150

±

1175

±

1200

±

1225

±

1250

±

1300

±

1350

±

1450

±

1650

±

in counts. Initial

40 Ar

2763477

2313

1378663

497

1433341

1116

2245492

1941

1516797

809

1503908

472

2553411

984

3560645

2195

2553455

2513

2297968

1309

1336208

638

1087395

550

1626977

911

458065

212

324995

259

251607

101

40Ar/36Ar = 297.

39Ar

41991

40

37580

21

38111

28

50700

15

32925

29

32078

23

57681

50

81111

66

57989

56

53005

19

31163

18

25234

10

35991

26

10906

10

11206

14

22062

18

2 ±0.5

38Ar

5766

19

4860

8

5372

25

8635

35

5605

3

5386

7

8818

18

12662

31

9157

2

8308

17

4965

25

4070

21

6073

20

1612

9

1058

10

459

6

37Ar

2444

11

3487

13

3931

9

6162

16

4137

13

4207

14

7674

8

11350

10

8700

12

8212

14

4679

4

3545

15

4840

14

1441

8

993

14

335

8

36Ar

2479

12

122

8

72

3

85

4

54

5

51

1

112

5

133

5

115

5

110

5

68

9

57

7

57

10

46

3

40

3

53

1

Precisions are at the 1 sigma level, and are from linear regression statistics. 

Trap current factors: 40 = 3.57 50 = 1 75 = 1 

Manifold factors: All = 1, Split 1 = 4.2, Split2 = 17.64, Split 3 = 74.09 

EA11 = 2.26, Esplitl = 9.49, Esplit2 - 39.87 

Sensitivity = 1.344 X 10-17 moles/count. Reproducibility limit = .25 %. Detection limit

Trap current

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

= 40 counts.

Manifold

ALL

SPLIT

SPLIT

SPLIT

SPLIT

SPLIT

ALL

ALL

ALL

ALL

ALL

ALL

ALL

ALL

ALL

ALL

1

1

2

2

1

24
Table 4B. RRNB-4QQ HORNBLENDE #57,58&59 RD74 v.9/21/99 14:34:58 16 Sep 1999

CORRECTIONS

Temp 39Ar 37Ar - K-derived Ca-derivec 

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar

850 49 55697 239 1 0 39

1000 44 79523 214 2 0 56

1050 44 89716 217 3 0 63

1075 59 140751 288 4 0 99

1100 38 94589 187 5 0 67

1125 37 96267 182 6 0 68

1125 67 175698 328 7 0 124

1150 95 260046 461 8 0 183

1175 68 199524 329 9 0 141

1200 62 188461 301 10 0 133

1225 36 107452 177 11 0 76

1250 29 81469 143 12 0 57

1300 42 111307 205 13 0 79

1350 13 33157 62 14 0 23

1450 13 22859 64 15 0 16

1650 26 7730 126 16 0 5

2 15

3 22

3 25

5 39

3 26

3 27

6 49

9 72

7 55

6 52

4 30

3 23

4 31

1 9

1 6

0 2

Cl-derivec

36Ar

2

1

2

2

2

2

2

4

3

2

1

1

2

0

0

0

initial

38Ar

463

19

9

8

5

4

11

11

11

11

7

6

5

7

6

10

All values are in counts and have been corrected for mass discrimination.

Table 4C. RRNB-400 HORNBLENDE #57,58&59 RD74 v.9/21/99 14::34:58 16 Sep 1999

MOLAR VALUES

Temperatun 40Ar* 39ArK 38Arc, 37Ca

(°C)

850 37.137920 0.565294 0.076348 0.784788

1000 77.810695 2.123694 0.247599 4.705992

1050 80.897015 2.153312 0.275595 5.308974

1075 532.296512 12.027860 1.892895 34.980639

1100 359.560410 7.810538 1.228584 23.507086

1125 84.882330 1.811619 0.280753 5.696049

1125 34.313440 0.775584 0.108550 2.475148

1150 47.848874 1.090510 0.156100 3.663301

1175 34.314006 0.779508 0.113042 2.810608

1200 30.880643 0.712461 0.102503 2.654695

1225 17.956257 0.418898 0.061367 1.513548

1250 14.612657 0.339257 0.050369 1.147516

1300 21.863822 0.483918 0.075397 1.567754

1350 6.155558 0.146643 0.019847 0.466995

1450 4.367075 0.150783 0.012319 0.321944

1650 3.379907 0.297216 0.002329 0.108870

36Arj Apparent Age

0.033278

0.005623

0.002578

0.010499

0.006318

0.001333

0.000825

0.000780

0.000772

0.000759

0.000506

0.000450

0.000330

0.000497

0.000454

0.000689

(Ma)

603.23

466.05

481.53

556.96

576.45

585.48

556.20

553.35

554.02

546.38

540.67

542.56

567.62

523.73

374.62

151.91

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

Precision

(Ma)

1.10

0.71

0.41

0.49

0.57

0.20

0.34

0.35

0.55

0.41

0.98

0.92

0.90

1.03

0.98

0.14

All gas quantities are in moles x 10~ 12 . 

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0. 

All precision estimates are at the one sigma level of precision. 

Ages of individual steps do not include error in the irradiation parameter J.

25
Table 4D. RRNB-4QQ HORNBLENDE #57,58&59 RD74 v.9/21/99 14:34:58 16 Sep 1999

Temperature 

°C

O/ 39 A _

/o Ar 

of total

Radiogenic 

Yield (%)

39 A

J = .008221 ± 0.5%

850

1000

1050

1075

1100

1125

1125

1150

1175

1200

1225

1250

1300

1350

1450

1650

Total Gas

NO PLATEAU

1.8

6.7

6.8

38.0

24.6

5.7

2.4

3.4

2.5

2.2

1.3

1.1

1.5

0.5

0.5

0.9

100.0

73.5

97.9

99.1

99.4

99.5

99.5

99.3

99.5

99.3

99.3

99.2

99.1

99.6

97.6

96.9

94.0

98.8

0.565294

2.123694

2.153312

12.027860

7.810538

1.811619

0.775584

1.090510

0.779508

0.712461

0.418898

0.339257

0.483918

0.146643

0.150783

0.297216

31.687096

40Ar*/39ArK Apparent 

K/Ca

Sample wt. -

48.301

35.857

37.215

43.997

45.796

46.637

43.928

43.666

43.727

43.029

42.509

42.681

44.979

40.975

28.074

10.687

43.199

0.4

0.2

0.2

0.2

0.2

0.2

0.2

0.2

0.1

0.1

0.1

0.2

0.2

0.2

0.2

1.4

0.2

Apparent 

K/C1

= .8118g

18

21

19

15

15

16

17

17

17

17

17

16

16

18

30

309

19

Apparent Age Precision 

Ma Ma

603.23

466.05

481.53

556.96

576.45

585.48

556.20

553.35

554.02

546.38

540.67

542.56

567.62

523.73

374.62

151.91

548.25

± 1.10

± 0.71

± 0.41

± 0.49

± 0.57

± 0.20

± 0.34

± 0.35

± 0.55

± 0.41

± 0.98

± 0.92

± 0.90

± 1.03

± 0.98

± 0.14

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10" 12 .

*** Below detection limit.

26
Figure 4A. Age spectrum for RRNB-400 hornblende. 

1 r 

.1

600

bfl

<

"8

500

400

0

RRNB-400 

HORNBLENDE

39Ar, RELEASED (%)

rv v x

cP

100

27
Figure 4B. Inverse isotope correlation diagram for RRNB-400 hornblende. Regressing all points. 

MSWD = 472.6, SUMS = 5671, initial 40Ar/36Ar = 491.6 ± 3.1, and apparent age = 523.9 ± 2.4 M; 

Deletion of points from the regression did not improve the results.

CO

o 

o 

o

o 

o

vcr

o 

o 

o

(N

O

o 

o

RRNB-400

.005 .01 .015 .02 .025 .03

39

28
Table 5A. YN-Pville Hornblende #2,3,4&5 RD93 v. 4/17/98 1 :55 :27PM 9/14/1999

RAW DATA

File# Temperature 40Ar 39Ar 38Ar 37Ar

35827 1050 4410143 38998 2267 79919

± 1660 37 11 55

35828 1075 3081986 28137 1519 54756

± 1740 30 8 36

35829 1100 3285204 30142 1573 58259

± 4210 18 9 101

35830 1125 2036088 18815 1000 36195

± 710 45 15 27

35831 1150 1511189 13178 666 25545

± 381 6 14 28

35832 1175 1691946 14322 699 27742

± 798 18 17 19

35833 1200 2296702 19401 1066 38315

± 3887 41 8 58

All values are in counts. Measured 40Ar/36Ar = 297.2 ± 0.5

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1 

Manifold factors: All = 1 Splitl = 3.3 Split2 = 10.89 

EA1I - 2 Esplitl = 6.6 Esplit2 = 21.78 

Sensitivity = 1.360 X 10" 17 moles/count. Reproducibility limit = .25 %. Detection

Table SB. YN-Pville Hornblende #2,3,4&5 RD93 v. 4/17/98 1 :55

CORRECTIONS

TWnn 39 Ar Ar kT rlfrivprl Pa-Hprivpr

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar

1050 15 156497 221 521 0 160 8

1075 11 107313 159 376 0 110 5

1100 12 114278 171 403 0 117 5

1125 7 71059 107 252 0 72 3

1150 5 50192 75 176 0 51 2

1175 6 54555 81 192 0 56 3

1200 8 75402 110 259 0 77 4

All values are in counts and have been corrected for mass discrimination.

36Ar

247

7

113

4

96

7

63

4

52

3

60

9

81

4

Trap current Manifold

200 BALL

200 ESPLIT

200 ESPLIT

200 ESPLIT

200 ESPLIT

200 ESPLIT

200 EALL

1

1

1

1

1

limit = 40 counts.

:27PM

36Ar

63

43

46

28

20

22

30

9/14/1999

Cl-derived initial

36Ar 38Ar

0 35

0 13

0 9

0 6

0 6

0 7

0 10

29
Table 5C. YN-Pville Hornblende #2,3,4&5 RD93 v. 4/17/98 1:55:27 PM 9/14/1999

MOLAR VALUES

Temperture 40Ar* 39ArK 38Arc , 37Ca 36Ar;

(°C)

1050 317.8672 2.804598 0.128272 17.114367 0.013381

1075 733.055499 6.678910 0.274884 38.716748 0.016816

1100 781.391147 7.155044 0.280411 41.217432 0.011983

1125 484.286772 4.466248 0.179376 25.622076 0.00819

1150 359.439608 3.128071 0.117751 18.092694 0.007658

1175 402.433719 3.399789 0.122189 19.659874 0.009091

1200 165.538379 1.395470 0.058816 8.232104 0.003689

All gas quantities are in moles x 10 l2 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Apparent Age

(Ma)

1050.982 ±

1030.114 ±

1027.959 ±

1022.018 ±

1066.967 ±

1090.763 ±

1092.602 ±

Precision

(Ma)

0.47

0.545

1.118

0.557

0.553

1.375

1.464

Table 5D. YN-Pville Hornblende #2,3,4&5 RD93 v. 4/17/98 1:55:27 PM 9/14/1999

Temperature % 39Ar Radiogenic 39ArK 40Ar*/39ArK Apparent Apparent

°C of total Yield (%) K/Ca K/C1

J - 0.007064 ± 0.5% Sample Wt =

1050 9.7 98.8 2.804598 111.928 0.09 53

1075 23.0 99.3 6.678910 109.013 0.09 59

1100 24.6 99.5 7.155044 108.714 0.09 62

1125 15.4 99.5 4.466248 107.891 0.09 60

1150 10.8 99.4 3.128071 114.184 0.09 64

1175 11.7 99.3 3.399789 117.580 0.09 67

1200 4.8 99.3 1.395470 117.844 0.09 57

Total Gas 100.0 99.4 29.028130 111.033 0.09 61

NO PLATEAU

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10"' 2 .

Apparent Age

Ma

1.0028g

1050.98 ±

1030.11 ±

1027.96 ±

1022.02 ±

1066.97 ±

1090.76 ±

1092.60 ±

1044.60

Precision

Ma

0.47

0.55

1.12

0.56

0.55

1.38

1.46

30
Apparent Age (Ma) 

^o 

o 

o 1

HH

O

r 

w

03

W 

O

f^ CD" 

W

O

W

O 

O

n
Figure 5B. Inverse isotope correlation diagram for YN-Pville hornblende. Points A,B,C,and D,

39 which contain 72.7% of the Ar released, were regressed. MSWD =1.015, SUMS = 2.03, initial

40 36 Ar/Ar = 1526.9 ± 140.1, and apparent age = 1008.7 ± 5.4 Ma.

w

(N

W00 

<N

»/ >

w

YN-Pville

.002 .004 .006 

3<

.008 .01

Ar/Ar

W/O POINTS EFG

32
Table 6A. LN-186 Phlogopite #36 RD77 v. 4/17/98 1:07:03 PM 9/14/1999

RAW DATA

File#

31267

31268

31269

31270

31271

31272

31273

31274

31275

31276

31277

Temperature 40Ar 39Ar 38Ar

850

±

900

±

925

±

950

±

1000

±

1050

±

1100

±

1150

±

1200

±

1250

±

1450

±

1008158 29012

697 51

1316000 38302

1471 38

896432 26112

178 31

799087 23090

402 47

963766 27989

402 28

1371337 39841

1938 41

2739550 79831

1081 73

3767261 109958

5024 119

3300685 96490

1810 46

939888 27436

588 21

441751 12733

218 18

All values are in counts. Measured 40Ar/36Ar = 296.7 ±

423

16

508

9

343

7

108

38

359

1 1

531

10

1050

13

1439

10

1273

10

374

11

91

5

0.5

37Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 - 2.62 200 = 1 

Manifold factors: All - 1 Split 1 =3.3 Split2 = 10.89 

EA11 = 2 Esplitl - 6.6 Esplit2 = 21.78 

Sensitivity = 1.00 X 10 l7 moles/count. Reproducibility limit = .25 %. Detection

36Ar

53

4

37

11

27

7

10

3

18

10

29

7

49

7

72

4

52

5

12

9

7

3

limit =

Trap current

200

200

200

200

200

200

200

200

200

200

200

40 counts.

Manifold

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

33
Table 6B. LN-186 Phlogopite #36 RD77 v. 4/17/98 1:07:03 PM 9/14/1999

CORRECTIONS

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar

850 79 0 165 390 0 0

900 104 0 218 515 0 0

925 71 0 149 351 0 0

950 63 0 132 311 0 0

1000 76 0 160 376 0 0

1050 109 0 227 536 0 0

1100 218 0 455 1074 0 0

1150 300 0 627 1479 0 0

1200 263 0 550 1298 0 0

1250 75 0 156 369 0 0

1450 35 0 73 171 0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

Cl-derived initial

36Ar

0

0

0

0

0

0

0

0

0

0

0

38Ar

10

7

5

2

3

5

9

14

10

2

1

All values are in counts and have been corrected for mass discrimination.

Table 6C. LN-186 Phlogopite #36 RD77 v. 4/17/98 1:07:03 PM 9/14/1999

MOLAR VALUES

Temperture 40Ar* 39ArK 38Arc , 37Ca

(°C)

850 20.159856 0.582309 0.000876 0.000000

900 26.315634 0.768768 0.000017 0.000000

925 17.925672 0.524109 0.000000 0.000000

950 15.979098 0.463453 0.000000 0.000000

1000 19.272125 0.561787 0.000000 0.000000

1050 27.422189 0.799660 0.000027 0.000000

1100 54.781895 1.602327 0.000000 0.000000

1150 75.332681 2.207012 0.000000 0.000000

1200 66.002700 1.936686 0.000000 0.000000

1250 18.794628 0.550672 0.000156 0.000000

1450 8.833561 0.255566 0.000000 0.000000

All gas quantities are in moles x 10~ 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

36Ari

0.001064

0.000748

0.000539

0.000208

0.000360

0.000586

0.000980

0.001445

0.001048

0.000232

0.000139

Apparent Age

(Ma)

406.89

405.43

404.95

409.73

407.27

406.85

406.12

405.39

405.18

406.10

410.35

±

±

±

±

±

±

±

±

db

db

db

Precision

(Ma)

0.50

0.97

0.86

0.51

1.09

0.76

0.31

0.50

0.26

1.01

0.85

34
Table 6D. LN-186 Phlogopite #36 RD77 v. 4/17/98 1:07:03 PM 9/14/1999

Temperature 

°C

J =007424

850

900 

925 

950 

1000 

1050 

1100 

1150 

1200 

1250 

1450 

Total Gas

% 39Ar Radiogenic 

of total Yield (%)

± 0.50 %

5.7

7.5 

5.1 

4.5 

5.5 

7.8 

15.6 

21.5 

18.9 

5.4 

2.5 

100.0

74.7% of gas

98.4

99.2 

99.1 

99.6 

99.4 

99.4 

99.5 

99.4 

99.5 

99.6 

99.5 

99.4

on plateau

39ArK 40Ar*/39ArK Apparent Apparent Apparent Age Precision 

K/Ca K/C1 Ma Ma

0.582309

0.768768 

0.524109 

0.463453 

0.561787 

0.799660 

1.602327 

2.207012 

1.936686 

0.550672 

0.255566 

10.252349

in 1000 through

34.080

33.943 

33.898 

34.346 

34.116 

34.076 

34.008 

33.940 

33.920 

34.006 

34.404 

34.007

1250 steps

Sample wt = 0.0778 g

1610 406.89

* * * 109769 405.43

* * * * * * 404.95

* * * * * * 409.73

* * * * * * 407.27 

* * * 72594 406.85

* * * * * * 406.12

* * * * * * 405.39

* * * * * * 405.18 

8531 406.10

* * * * * * 410.35 

* * * 14443 406.11

Plateau Age =405.72 ± 2

±

± 

± 

± 

± 

± 

± 

± 

± 

± 

±

.03

0.50

0.97 

0.86 

0.51 

1.09 

0.76 

0.31 

0.50 

0.26 

1.01 

0.85

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10" 12 .

*** Below detection limit.

35
Figure 6A. Age spectrum for Ln-186 phlogopite.

425

400

=

&,

OH 375

350 0

LN-186

PHLOGOPITE

PLATEAU AGE = 405.7 ± 2.0 Ma

39Ar, Is. RELEASED (%

I I

100

36
Figure 6B. Inverse isotope correlation diagram for RR89-28 biotite. All points which contain 

100% of the 39Ar released, were regressed. MSWD = 0.803, SUMS = 7.288, initial 40Ar/36Ar = 

395.74 ± 685.22, and apparent age = 404.7 ± 2.3 Ma.

W 

o

^O" 

m

W

<N

LN-186

.005 .01 .015 

39. 4Q

.02 .025 .03

Ar/AY

37
Table 7A. K92-7-15B Phlogopite #11RD93 v. 4/17/98 2:18:24 PM 9/14/1999

RAW DATA

File#

35630

35631

35632

35633

35634

35635

35636

35637

35638

35639

35640

35641

Temperature

850

±

900

±

925

+

950

±

1000

±

1050

±

1100

±

1125

±

1150

±

1200

±

1250

±

1450

±

40Ar

1586752

565

2052681

652

1133461

229

606946

263

700138

561

1181176

417

1450354

1670

937140

730

865558

401

1734023

751

1560855

1490

274575

156

All values are in counts. Measured 40Ar/36Ar =

39Ar

42035

13

56764

14

31438

14

16544

13

18720

34

31422

12

39153

60

25836

16

24123

8

48792

34

44163

28

7603

2

297.2 ± 0.5

38Ar

621

8

837

7

449

9

158

10

121

40

487

18

583

10

399

7

359

10

695

11

635

15

69

1 1

37Ar

3672

8

157

19

63

7

49

11

95

2

129

13

112

7

97

14

85

14

93

7

137

16

69

6

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1 

Manifold factors: All - 1 Split 1 - 3.3 Split2 = 10.89 

EA11 = 2 Esplitl =6.6 Esplit2 = 21.78 

Sensitivity = 1.3604 X 10~' 7moles/count. Reproducibility limit = .25 %. Detection

36Ar

334

2

280

7

129

7

76

5

144

6

287

2

276

4

158

9

143

7

212

2

123

4

46

10

limit

Trap current

200

200

200

200

200

200

200

200

200

200

200

200

= 40 counts.

Manifold

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

38
Table 7B. K92-7-15B Phlogopite #1 1RD93 v. 4/17/98 2:18:24 PM 9/14/1999

CORRECTIONS

Temp

850 

900 

925 

950 

1000 

1050 

1100 

1125 

1150 

1200 

1250 

1450

All values

39Ar 37Ai 

decay deca

K.

v 40Ar

-d<

38

14 5763 239 

19 247 323 

11 99 179 

6 77 94 

6 150 107 

11 203 179 

13 176 223 

9 153 147 

8 134 137 

17 147 278 

15 217 251 

3 108 43

it*i\/pri

Ar 37Ar

564 0 

762 0 

422 0 

222 0 

251 0 

422 0 

526 0 

347 0 

324 0 

655 0 

593 0 

102 0

Pa

39Ar

6 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0

-der

38 A,r 36Ar

Cl-derived 

36Ar

0 3 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0

initial

38Ar

62 

53 

24 

14 

27 

54 

52 

30 

27 

40 

23 

9

are in counts and have been corrected for mass discrimination.

Table 1C. K92-7-15B Phlogopite #1 1RD93 v. 4/17/98 2:18:24PM 9/14/1999

MOLAR VALUES

Temperture 40Ar* 39ArK 38Ar 37Ca 36ATi Apparent Age

(°C) (Ma)

850

900

925

950

1000

1050

1100

1125

1150

1200

1250

1450

114.355841

147.933989

81.686974

43.741913

50.458246

85.126290

104.525438

67.538466

62.379514

124.968387

112.488283

19.788213

3.034778

4.098811

2.270094

1.194570

1.351736

2.268929

2.827156

1.865537

1.741864

3.523170

3.188898

0.548967

0

0

0

0

0

0

0

0

0

0

0

0

.008695 0,

.009337 0

.003819 0

.000000 0

.000000 0

.008655 0

.007973 0

.005964 0

.004543 0

.005926 0

.004830 0

.000000 0

.683052

.029277

.011707

.009090

.017704

.024008

.020863

.018114

.015896

.017342

.025595

.012813

0,

0.

0,

0.

0.

0.

0,

0,

0.

0.

0,

0.

.023997

.020283

.009359

.005492

.010401

.020786

.020015

.011450

.010387

.015393

.008921

.003316

423.

415

416

422

420

417

418

412

409

410

413

411

.19

.54

.99

.26

.09

.48

.22

.96

.31

.70

.59

.59

±

±

±

±

±

±

±

±

±

±

±

±

Precision

(Ma)

0.22

0.43

0.76

0.95

1.10

0.23

0.57

1.16

0.93

0.20

0.46

4.25

All gas quantities are in moles x 10~ 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

39
Table 7D. K92-7-15B Phlogopite #1 1RD93 v. 4/17/98 2:18:24 PM 9/14/1999

Temperature

°C

J = 0.007480 ± 

850

900

925

950

1000

1050

1100

1125

1150

1200

1250

1450

Total Gas

No age plateau

% 39Ar Radiogenic 

of total Yield (%)

0.05% 

10.9

14.7

8.1

4.3

4.8

8.1

10.1

6.7

6.2

12.6

11.4

2.0

100.0

Ages calculated assuming an

93.8

95.9

96.6

96.3

93.9

92.8

94.3

95.0

95.1

96.4

97.7

95.0

95.4

initial 40

3.

4.

2.

1.

1.

2.

2.

1.

1.

3.

3.

0.

27

39ArK 40Ar*/39ArK

034778

098811

270094

194570

351736

268929

827156

865537

741864

523170

188898

548967

.914510

35.345

34.630

34.766

35.259

35.055

34.811

34.880

34.389

34.050

34.179

34.448

34.261

34.669

Apparent 

K/Ca

Apparent 

K/C1

Sample wt = 

2.3 845

72.8

100.8

68.3

39.7

49.1

70.5

53.6

57.0

105.6

64.8

22.3

63.4

1062

1438

* * *

* * *

634

858

757

928

1439

1598

* * *

976

Apparent Age Precision 

Ma Ma

0.1017g 

423.19

415

416

422

420

417

418

412

409

410

413

411

415

.54

.99

.26

.09

.48

.22

.96

.31

.70

.59

.59

.96

±

±

±

±

±

±

±

±

±

±

±

±

0.22

0.43

0.76

0.95

1.10

0.23

0.57

1.16

0.93

0.20

0.46

4.25

Ar/36Ar = 295.5 ± 0.

All precision estimates are at the one sigma level. 

Ages of individual steps do not include error in the irradiation parameter J. 

No error is calculated for the total gas age. 

39 ArK gas quantities are in moles x 10"' 2 .

40
u 

L.

c

0

UJ

SO

>

?T

S

r 

w 

>w 

w 

O

3

Apparent Age (Ma) 

0 OJ -fc. -fc. 

h o o to 

5 L/l O Ul 

III

~~ ^5^

ffi ^> 

t-" to

°7J

O

1

i >

_ hd bd > H H 

W

u

D n

]
Figure 7B. Inverse isotope correlation diagram for K92-7-15B phlogopite. Points D,E,F,G,H,I,J,K,

39 and L, which contain 62.0% of the vAr released, were regressed. MSWD =1.151, SUMS = 6.909,

40 /36 initial Ar/JOAr = 459.97 ± 58.65, and apparent age = 403.8 ± 4.7 Ma.

<N

O 

O 

O

O 

O 

O

W 

od

K92-7-15B

.005 .01 .015 .02 .025 .03

W/O POINTS ABCD

42
Table 8A. BR-138 Muscovite #46 RD72 v. 4/17/98 11:29:28 AM 9/14/1999

RAW DATA

File# Temperature 40Ar 39Ar 38Ar

26472 900 1646559 80492 972

± 455 60 23

26473 950 989289 51131 561

± 431 3 15

26474 1000 1624965 83152 882

± 1140 53 24

26475 1025 1871118 94674 1030

± 1375 92 18

26476 1050 1814471 91332 908

± 1034 85 32

26478 1100 2679652 132888 1721

± 1841 111 15

26479 1150 1706138 82723 866

± 1477 35 7

26480 1200 1042259 49745 537

± 339 47 15

All values are in counts. Measured 40Ar/36Ar = 295.7 ± 0.5

37Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

36Ar

122

4

39

2

34

4

36

6

34

4

41

4

22

7

25

3

Trap current

200

200

200

200

200

200

200

200

Manifold

ALL

ALL

ALL

ALL

ALL

ALL

ALL

ALL

Precisions are at the 1 sigma level and are from linear regression statistics.

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1

Manifold factors: All = 1 Splitl = 3.3 Split2 = 10.89

EA11 = 2 Esplitl =6.6 Esplit2 = 21.78

Sensitivity = 1.344 X 10' 17 moles/count. Reproducibility limit = .25 %.

Table 8B. BR-138 Muscovite #46 RD72 v. 4/17/98 11:29

Detection

:28AM

limit = 40 counts.

9/14/1999

CORRECTIONS

Temp 39Ar 37Ar - K-derived - 

(°C) decav decay 4°Ar 38Ar 37Ar 39Ar

900 127 0 459 1082 0 0

950 81 0 291 687 0 0

1000 132 0 474 1118 0 0

1025 150 0 539 1272 0 0

1050 145 0 520 1228 0 0

1100 211 0 757 1786 0 0

1150 131 0 471 1112 0 0

1200 79 0 283 669 0 0

Ca-derivec

38Ar

0

0

0

0

0

0

0

0

36Ar

0

0

0

0

0

0

0

0

Cl-derived

36Ar

0

0

0

0

0

0

0

0

initial

38Ar

23

7

6

7

6

8

4

5

All values are in counts and have been corrected for mass discrimination.

43
Table 8C. BR-138 Muscovite #46 RD72 v. 4/17/98 11:29:28 AM 9/14/1999

MOLAR VALUES

Temperture 

(°C)

900

950

1000

1025

1050

1100

1150

1200

40Ar*

22.123592

13.292130

21.833160

25.140583

24.379497

36.004342

22.924155

14.004155

39ArK 38Arcl 37Ca

1.085084

0.689275

1.120937

1.276264

1.231221

1.791416

1.115156

0.670599

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

36Afi Apparent Age Precision 

(Ma) (Ma}

0.001654

0.000533

0.000459

0.000486

0.000460

0.000549

0.000297

0.000335

325.97 ±

312.72 ±

317.25 ±

320.69 ±

322.26 ±

327.01 ±

334.03 ±

337.85 ±

0.24

0.19

0.31

0.37

0.25

0.24

0.45

0.32

All gas quantities are in moles x 10~' 2 .

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 8D. BR-138 Muscovite #46 RD72 v. 4/17/98 11:29:28 AM 9/14/1999

Temperature 

°C

% 39Ar 

of total

Radiogenic 39ArK 40Ar*/39ArK Apparent Apparent Apparent Age Precision 

Yield (%)____________________K/Ca K/C1_____Ma_______Ma

J = 0.009933 ± 0.05% 

900 12.100 

950

1000

1025

1050

1100

1150

1200 

Total Gas

No age plateau

7.700

12.500

14.200

13.700

19.900

12.400

7.500

100.000

	Sample wt = 0.2686

97.800 1.085084 19.938 * * *

98.800 0.689275 19.056 * * *

99.400 1.120937 19.357 *** **<

99.400 1.276264 19.586 * * *

99.400 1.231221 19.691 * * *

99.500 1.791416 20.008 *** **'

99.600 1.115156 20.478 *** **^

99.300 0.670599 20.735 * * *

99.200 8.979952 19.854 * * *

325.97 ± 

312.72 ± 

317.25 ± 

320.69 ± 

322.26 ± 

327.01 ± 

334.03 ± 

337.85 ± 

324.71

0.24

0.19

0.31

0.37

0.25

0.24

0.45

0.32

Ages calculated assuming an initial 40Ar/36Ar = 295.5 ± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x I0"' 2 .

*** Below detection limit._______________________

44
Figure 8. Age spectrum for BR-873 muscovite.

400

375

350

OH 

OH

325

300 0

BR-138 

MUSCOVITE

I I

39An, RELEASED (%) iv ^ /

100

45
Table 9A. BR-873 Muscovite #49 RD 74 v. 4/17/98 10:35:04 AM 9/14/1999

RAW DATA

File# Temperature 40Ar 39Ar 38Ar

25198 900 915478 36428 539

± 596 32 14

25199 950 1155025 45520 564

± 884 29 22

25200 1025 1651781 65073 794

± 440 56 20

25201 1025 1986977 77844 971

± 1599 75 9

25203 1050 1513314 59164 755

± 609 23 10

25204 1100 1472675 58278 722

± 646 33 3

25205 1150 1843529 73235 908

± 1817 58 5

25207 1200 3470535 136746 1772

± 1536 64 9

25209 1250 2718429 104187 1396

± 1205 39 8

All values are in counts. Measured 40Ar/36Ar = 296.5 ± 0.5

37Ar

3

6

0

6

4

4

0

6

0

8

19

7

88

8

249

6

69

8

36Ar

195

7

161

3

70

3

130

3

149

4

124

6

111

4

127

8

220

3

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 3.57 100 = 2.15 200 = 1 

Manifold factors: All = 1 Splitl = 4.2 Split2 = 10.89 

EA11 = 2 Esplitl = 6.6 Esplit2 = 21.78 

Sensitivity = 2.15 X 10" 17 moles/count. Reproducibility limit = .25 %. Detection limit = 40

Table 9B. BR-873 Muscovite #49 RD 74 v. 4/17/98 10:35 :04AM

Trap current Manifold

200 ALL

200 ALL

200 SPLIT 1

200 ALL

200 ALL

200 ALL

200 ALL

200 ALL

200 ALL

counts.

9/14/1999

CORRECTIONS

Temp 39Ar 37Ar ~ K-derived 

(°C) decay decav 4°Ar 38Ar 37Ar 39Ar

900 14 7 207 489 0 0

950 18 0 259 611 0 0

1025 25 7 370 873 0 0

1025 30 0 443 1044 0 0

1050 23 0 336 794 0 0

1100 23 37 331 782 0 0

1150 28 171 416 983 0 0

1200 53 487 778 1835 0 0

1250 41 135 593 1398 0 0

Ca-derivec

38Ar

0

0

0

0

0

0

0

0

0

36Ar

0

0

0

0

0

0

0

0

0

Cl-derived initial

36Ar 38Ar

0 37

0 30

0 13

0 24

0 28

0 23

0 21

0 24

0 41

All values are in counts and have been corrected for mass discrimination.

46
Table 9C. BR-873 Muscovite #49 RD 74 v. 4/17/98 10:35:04 AM 9/14/1999

MOLAR VALUES

Temperatun 40Ar* 39ArK 38Arc, 37Ca 36Ari

(°C)

900 19.678318 0.784171 0.001896 0.000219 0.004211

950 24.827467 0.979894 0.000000 0.000000 0.003479

1025 149.122436 5.883333 0.000000 0.000991 0.006377

1025 42.710481 1.675705 0.000000 0.000000 0.002815

1050 32.529025 1.273589 0.000000 0.000000 0.003209

1100 31.655390 1.254525 0.000000 0.001202 0.002679

1150 39.626914 1.576485 0.000000 0.005586 0.002399

1200 74.599780 2.943658 0.000000 0.015874 0.002738

1250 58.433487 2.242784 0.000891 0.004409 0.004738

All gas quantities are in moles x 10"' 2 . 

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Apparent Age

(Ma)

323.00

332.79

342.01

341.58

339.15

336.72

337.77

342.52

347.02

±

±

±

±

±

±

±

±

±

Precision

(Ma)

0.75

0.37

0.20

0.30

0.30

0.39

0.36

0.26

0.19

Table 9D. BR-873 Muscovite #49 RD 74 v. 4/17/98 10:35:04 AM 9/14/1999

Temperature % 39Ar Radiogenic 39ArK 40Ar*/39ArK Apparent Apparent 

°C of total Yield (%) K/Ca K/C1

J =0.008341 ± 0.25% Sample wt = 0.0743

900 4.2 93.7 0.784171 23.508 1858.4 1001

950 5.3 95.9 0.979894 24.288 * * * 

1025 31.6 98.7 5.883333 25.026 3088.2 * * *

1025 9.0 98.1 1.675705 24.992 * * *

1050 6.8 97.1 1.273589 24.797 * * * 

1100 6.7 97.5 1.254525 24.602 542.7

1150 8.5 98.2 1.576485 24.687 146.8

1200 15.8 98.9 2.943658 25.068 96.4

1250 12.0 97.6 2.242784 25.430 264.5 6090

Total Gas 100.0 98.0 18.614144 24.902 1150.5 776

NO PLATEAU

Apparent Age 

Ma

323.00 

332.79 

342.01 

341.58 

339.15 

336.72

337.77

342.52

347.02

340.46

± 

± 

± 

± 

± 

±

±

±

±

Precision 

Ma

0.75 

0.37 

0.20 

0.30 

0.30 

0.39

0.36

0.26

0.19

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10" 12 .

*** Below detection limit. ________

47
Figure 9. Age spectrum for BR873 muscovite.

400

375

S» 350

5

a,

325

300

BR873 

MUSCOVITE

I___I I I I

0

39 AL RELEASED (%) Is. v '

100

48
Table 10A. BR-904 MUSCOVITE #51RD87 v 4/17/98 13:28:54

RAW DATA

File# Temperature 40Ar 39Ar 38Ar 37Ar

32969 850 1107530 51857 696 0

± 894 50 19 16

32970 900 2602122 113420 1438 0

± 2628 106 3 18

32971 950 4485784 193036 2432 0

± 3027 129 12 23

32972 1000 2225805 96496 1222 0

± 3591 179 13 20

32973 1050 2634300 112618 1419 0

± 1848 83 10 12

32974 1100 4098575 174596 2206 0

± 3162 60 13 29

32975 1150 915235 38378 487 1

± 358 4 17 10

32976 1200 319084 13011 78 8

± 24 20 15 15

32977 1250 129120 5020 42 27

All values are in counts. Measured 40Ar/36Ar = 297.2 ± 0.5

Precisions are at the 1 sigma level and are from linear regression statistics.

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1

Manifold factors: All = 1 Splitl = 3.3 Split2 = 10.89

EA11 = 2 Esplitl = 6.6 Esplit2 - 21.78 

Sensitivity = 1.00 X 10~ 17 moles/count. Reproducibility limit = .25 %. Detection li

Table 10B. BR-904 MUSCOVITE #51RD87 v 4/17/98 13:28:54

CORRECTIONS

Temp 39Ar 37Ar - K-derived Ca-derivec

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar

850 22 0 295 696 000

900 49 0 645 1523 000

950 84 0 1098 2592 000

1000 42 0 549 1295 000

1050 49 0 641 1512 000

1100 76 0 994 2344 000

1150 17 2 218 515 000

1200 6 19 74 175 000

1250 2 64 29 67 0 0 0

All values are in counts and have been corrected for mass discrimination.

14

36Ar

88

5

40

4

50

4

26

12

31

7

19

8

9

5

5

5

6

mit = A

14

36Ar

0

0

0

0

0

0

0

0

0

Sep 1999

Trap current

200

200

200

200

200

200

200

200

200

10 counts.

Sep 1999

Cl-derived

36Ar

0

0

0

0

0

0

0

0

0

Manifold

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

initial

38Ar

17

8

9

5

6

4

2

1

1

49
Table 10C. BR-904 MUSCOVITE #51RD87 v 4/17/98 13:28:54 14 Sep 1999

MOLAR VALUES

Temperture 40Ar* 39ArK 38Arcl 37Ca 36Ar,

(°C)

850 22.144690 1.039087 0.000362 0.000000 0.001776

900 52.029529 2.272636 0.000000 0.000000 0.000803

950 89.693717 3.867938 0.000000 0.000000 0.001009

1000 44.505118 1.933530 0.000000 0.000000 0.000517

1050 52.673190 2.256574 0.000000 0.000000 0.000626

1100 81.951624 3.498457 0.000000 0.000000 0.000382

1150 18.300325 0.769005 0.000000 0.000046 0.000184

1200 6.380206 0.260698 0.000000 0.000550 0.000101

1250 2.581830 0.100595 0.000000 0.001830 0.000112

All gas quantities are in moles x 10" 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

Table 10D. BR-904 MUSCOVITE #51 RD87 v 4/17/98 13:28:54 14

Temperature % 39Ar Radiogenic 39ArK 40Ar*/39ArK Apparent Apparent

°C of total Yield (%) K/Ca K/C1

J = 009055 ± 0.5% Sample wt = 0.1 026 g

850 6.5 97.6 1.039087 20.807 *** 6939

900 14.2 99.5 2.272636 22.789 *** ***

950 24.2 99.7 3.867938 23.112 *** ***

1000 12.1 99.7 1.933530 22.939 *** ***

1050 14.1 99.6 2.256574 23.260 *** ***

1100 21.9 99.9 3.498457 23.393 *** ***

1150 4.8 99.7 0.769005 23.727 8688.61 ***

1200 1.6 99.5 0.260698 24.359 246.50 ***

1250 0.6 98.7 0.100595 25.336 28.59 ***

Total Gas 100.0 99.5 0.000000 23.042 421.84 451

NO PLATEAU

Apparent Age

(Ma)

311.39 ±

338.44 ±

342.80 ±

340.46 ±

344.80 ±

346.59 ±

351.09 ±

359.57 ±

372.60 ±

Sep 1999

Apparent Age

Ma

311.39 ±

338.44 ±

342.80 ±

340.46 ±

344.80 ±

346.59 ±

351.09 ±

359.57 ±

372.60 ±

341.85

Precision

(Ma)

0.44

0.35

0.23

0.70

0.34

0.31

0.55

1.60

7.27

Precision

Ma

0.44

0.35

0.23

0.70

0.34

0.31

0.55

1.60

7.27

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10~ 12 .

*** Below detection limit. __

50
Figure 10. Age spectrum for BR-904 muscovite.

400

375

350

Q.

-

325

300

0

BR-904 

MUSCOVITE

39Ar, RELEASED (%) K. ^> /

100

51
Table 11A. CBR-10-92 MUSCOVITE #28RD93 v 4/17/98

RAW DAT;

File # Temperature 40Ar 39Ar 38Ar

35749 850 1465766 50666 736

± 842 43 11

35750 900 3104789 108749 1472

± 1205 28 3

35751 950 4367695 153545 2044

± 1377 34 5

35752 1000 3672564 128668 1739

± 3045 144 7

35753 1050 1727193 59738 826

± 700 87 5

35754 1100 2233937 77394 1068

± 533 31 8

35755 1150 1504698 50955 697

± 2009 8 17

All values are in counts. Measured 40Ar/36Ar = 297.2 ± 0.5

Precisions are at the 1 sigma level and are from linear regression statistics 

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1 

Manifold factors: All = 1 Splitl = 3.3 Split2 - 10.89 

EAI1 = 2 Esplitl =6.6 Esplit2 = 21.78 

Sensitivity = 3.604 X 10" 17 moles/count. Reproducibility limit = .25 %.

Table 11B. CBR-10-92 MUSCOVITE #28RD93 v 4/17/98

CORRECTIONS

T> 39 A » 37 A- \r j j

Temp Ar Ar K-denved 

(°C) decay decay 40Ar 38Ar 37Ar 39Ar

850 18 52 288 680 0 0

900 39 40 619 1460 0 0

950 55 120 874 2061 0 0

1000 46 111 732 1727 0 0

1050 22 143 340 802 0 0

1100 28 103 440 1039 0 0

1150 18 222 290 684 0 0

All values are in counts and have been corrected for mass discrimination.

14:28

V

37Ar

30

13

23

7

69

14

64

11

83

10

60

3

128

7

Detection

14:28

Ca-derivec

38Ar

0

0

0

0

0

0

0

:15

36Ar

170

5

161

9

167

5

215

5

152

6

155

6

150

4

limit =

:15

36Ar

0

0

0

0

0

0

0

14 Sep 1999

Trap current

200

200

200

200

200

200

200

40 counts.

14 Sep 1999

Cl-derived

36Ar

0

0

0

0

0

0

0

Manifold

EALL

EALL

EALL

EALL

EALL

EALL

EALL

initial

38Ar

32

30

31

40

29

29

28

52
Table 11C. CBR-10-92 MUSCOVITE #28RD93 v 4/17/98 14:28:15 14 Sep 1999

MOLAR VALUES

Temperatun 

(°C)

850

900

950

1000

1050

1100

1150

40Ar*

105.631663

223.748577

314.760471

264.665622

124.471576

160.990411

108.437735

39ArK

3.658588

7.852693

11.087457

9.291044

4.313640

5.588577

3.679401

38 Ar Arci

0.006465

0.003359

0.001475

0.004125

0.003996

0.004423

0.003135

37Ca

0.005901

0.004526

0.013677

0.012682

0.016292

0.011775

0.025347

36ATi

0.012352

0.011653

0.012118

0.015570

0.011027

0.011235

0.010884

Apparent Age 

(Ma)

338.23 ±

340.22 ±

340.35 ±

339.52 ±

340.72 ±

341.97 ±

346.21 ±

Precision 

(Ma)

0.36

0.29

0.15

0.29

0.37

0.25

0.51

All gas quantities are in moles x 10" 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 11D. CBR-10-92 MUSCOVITE #28RD93 v 4/17/98 14:28:15 14 Sep 1999

Temperature 

°C

1 = 0.007398

850

900

950

1000

1050

1100

1150

Total Gas

% 39Ar 

of total

± 0.5%

8.0

17.3

24.4

20.4

9.5

12.3

8.1

100.0

Radiogenic 

Yield (%)

39 A r

ATK 40Ar*/39ArK Apparent 

K/Ca

Sample wt =

96.5

98.5

98.9

98.3

97.4

97.9

97

98.1

3.658588

7.852693

11.087457

9.291044

4.313640

5.588577

3.679401

45.471400

27.875

28.055

28.066

27.991

28.100

28.213

28.597

28.098

322.39

902.18

421.53

380.97

137.68

246.80

75.48

411.87

Apparent 

K/C1

0.1017 g

1370

5658

18192

5451

2613

3058

2841

7490

Apparent Age Precision 

Ma Ma

338.23

340.22

340.35

339.52

340.72

341.97

346.21

340.70

±

±

±

±

±

±

±

0.36

0.29

0.15

0.29

0.37

0.25

0.51

70.13% of gas on plateau in 850 through 1000 steps 

71.57% of gas on plateau in 900 through 1050 steps

Plateau Age =339.88 ± 1.73 

Plateau Age =340.20 ± 1.73

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10" 12 .

*** Below detection limit. ______________________

53
Figure 11. Age spectrum for CBR-10-92 muscovite.

400

375

8> 350

<D

3

a,

325

300

0

CBR-10-92 

MUSCOVITE

39

I I

ArK RELEASED (%) 100

54
Table 12A. T185B MUSCOVITE#26RD72 MUSCOVITE v4/17/98 11:46:48 14 Sep 1999

RAW DATA

File# Temperature 40Ar 39Ar 38Ar

25174 900 969702 50625 719

± 572 21 9

25175 950 1109247 58513 727

± 217 43 10

25176 1000 2805749 141309 1866

± 923 67 12

25178 1025 4484643 219678 2849

± 2182 163 7

25180 1050 3671691 181161 2370

± 1756 135 15

25181 1100 3451949 171990 2244

± 2284 160 14

25183 1150 3761799 187484 2421

± 3374 116 16

25185 1250 1709831 83555 962

± 462 42 1 1

25186 1250 3365326 162342 2092

± 1555 55 8

All values are in counts. Measured 40Ar/36Ar = 296.7 ± 0.5

37Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

36Ar

190

10

52

8

89

2

87

2

64

5

53

5

47

4

18

2

37

3

Trap current Manifold

200 ALL

200 ALL

200 ALL

200 ALL

200 ALL

200 ALL

200 ALL

200 SPLIT 1

200 ALL

Precisions are at the 1 sigma level and are from linear regression statistics.

Trap current factors: 40 = 3.57 100 = 2.15 200 = 1

Manifold factors: All = 1 Splitl = 4.2 Split2 = 17.65

EA11 = 2 Esplitl =6.6 Esplit2 = 21.78 

Sensitivity = 2.150 X 10" 17 moles/count. Reproducibility limit = .25 %.

Table 12B. Tl 85B MUSCOVITE #26RD72 MUSCOVITE

Detection limit =

v 4/1 7/98 11

40 counts.

:46:48 14 Sep 1999

CORRECTIONS

Temp 39Ar 37Ar - K-derived 

(°C) decay decay 40Ar 38Ar 37Ar 39Ar

900 49 0 288 680 0 0

950 56 0 333 785 0 0

1000 136 0 804 1897 0 0

1025 211 0 1250 2949 0 0

1050 174 0 1031 2432 0 0

1100 165 0 979 2309 0 0

1150 180 0 1067 2517 0 0

1250 80 0 475 1122 0 0

1250 156 0 924 2179 0 0

38Ar

0

0

0

0

0

0

0

0

0

36Ar

0

0

0

0

0

0

0

0

0

Cl-derived initial

36Ar 38Ar

0 36

0 10

0 17

0 16

0 12

0 10

0 9

0 3

0 7

All values are in counts and have been corrected for mass discrimination.

55
Table 12C. T185B MUSCOVITE#26RD72 MUSCOVITE v4/17/98 11:46:48 14 Sep 1999

MOLAR VALUES

Temperature 40Ar* 39ArK 38Arc , 37Ca

(°C)

900 20.842404 1.090408 0.001631 0.000000

950 23.841661 1.260294 0.000000 0.000000

1000 60.306310 3.043627 0.000000 0.000000

1025 96.392940 4.731616 0.000000 0.000000

1050 78.919194 3.901998 0.000000 0.000000

1100 74.195869 3.704477 0.000000 0.000000

1150 80.855742 4.038189 0.000000 0.000000

1250 154.354803 7.558680 0.000000 0.000000

1250 72.334640 3.496659 0.000000 0.000000

All gas quantities are in moles x 10~ 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 12D. Tl 85B MUSCOVITE #26RD72 MUSCOVITE v

36ATi

0.004088

0.001118

0.001914

0.001888

0.001374

0.001154

0.001023

0.001674

0.000804

4/17/98 11

Temperature % 39Ar Radiogenic 39ArK 40Ar*/39ArK Apparent Apparent

°C of total Yield (%) K/Ca K/C1

J =0.009954 ± 0.25% Sample v

900 3.3 94.2 1.090408 18.006

950 3.8 98.6 1.260294 18.655

1000 9.3 99.1 3.043627 19.628

1025 14.4 99.4 4.731616 20.254

1050 11.9 99.5 3.901998 20.121

1100 11.3 99.5 3.704477 19.937

1150 12.3 99.6 4.038189 19.948

1250 23.0 99.7 7.558680 20.355

1250 10.7 99.7 3.496659 20.619

Total Gas 100.0 99.3 32.825948 20.033

NO PLATEAU

vt- 0.1012 g

1617

54

Apparent Age

(Ma)

297.42

307.27

321.95

331.33

329.34

326.58

326.75

332.84

336.77

:46:48 14

Apparent Age

Ma

297.42

307.27 

321.95

331.33 

329.34

326.58 

326.75

332.84 

336.77

328.02

Precision

±

±

±

±

±

±

±

±

±

Sep

(Ma)

0.95

0.62

0.12

0.15

0.19

0.24

0.29

0.12

0.16

1999

Precision

±

± 

±

±

±

± 

±

± 

±

Ma

0.95

0.62 

0.12

0.15 

0.19

0.24 

0.29

0.12 

0.16

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10"' 2 .

*** Below detection limit. __

56
Figure 12. Age spectrum for T185B muscovite.

400

375

350

W 

60

325

£ 

a,

£

300

275

0

T185B 

MUSCOVITE

39 Ar, RELEASED (%)

IV x '

I I

100

57
Table 13A. T65 MUSCOVITE #25RD72 v 4/17/98 1 1:55:39

RAW DATA

File# Temperature 40Ar 39Ar 38Ar 37Ar

25150 850 1070116 53080 720 0

± 5177 238 12 0

25152 950 4389437 212211 2857 0

± 121 232 6 0

25154 975 612602 29815 359 0

± 152 36 8 0

25156 1025 602018 29434 370 0

± 390 29 10 0

25158 1050 1025416 50593 611 0

± 414 42 10 0

25159 1050 3249215 161086 2220 0

± 2845 141 29 0

25161 1100 4190246 211849 2886 0

± 16398 667 6 0

25163 1150 4052638 200503 2644 0

± 3375 198 5 0

25164 1200 4769684 232728 3033 0

± 1059 186 23 0

25165 1250 1807182 86515 1023 0

± 1406 79 19 0

All values are in counts. Measured 40Ar/36Ar = 296.5 ± 0.5

Precisions are at the 1 sigma level and are from linear regression statistics.

Trap current factors: 40 = 3.57 100 = 2.15 200 = 1

Manifold factors: All = 1 Split 1 =3.3 Split2 - 10.89

EA11 = 2.26 Esplitl - 9.49 Esplit2 = 39.87 

Sensitivity = 2.150 X 10" 17 moles/count. Reproducibility limit = .25 %. Detection

Table 13B. T65 MUSCOVITE #25RD72 v 4/17/98 11:55:39

CORRECTIONS

Temp 39Ar 37Ar - K-derived - Ca-derivec

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar

850 50 0 302 713 000

950 199 0 1208 2849 000

975 28 0 170 400 000

1025 28 0 167 395 000

1050 48 0 288 679 000

1050 151 0 917 2162 000

1100 199 0 1205 2844 000

1150 189 0 1141 2692 000

1200 219 0 1324 3124 000

1250 81 0 492 1161 000

All values are in counts and have been corrected for mass discrimination.

14Sepl999

36Ar Trap current

141 200

8

559 200

1 1

44 200

5

30 200

3

28 200

3

152 200

4

302 200

13

122 200

4

111 200

7

100 200

6

limit = 40 counts.

14Sepl999

 Cl-derived

36Ar 36Ar

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

Manifold

ALL

ALL

ALL

SPLIT 1

SPLIT 1

ALL

ALL

ALL

ALL

ALL

initial

38Ar

26

105

8

6

5

28

57

23

21

19

58
Table 13C. T65 MUSCOVITE #25RD72 v 4/17/98 11:55:39 14 Sep 1999

MOLAR VALUES

Temperature

850

950

975

1025

1050

1050

1100

1150

1200

1250

40Ar*

23.001004

94.346940

13.167293

54.347132

92.569092

69.838419

90.064363

87.107181

102.519740

38.843838

39ArK

1.143256

4.570677

0.642174

2.662625

4.576665

3.469546

4.562901

4.318517

5.012588

1.863402

38 ArArC i

0.000756

0.002536

0.000000

0.000000

0.000000

0.001927

0.002221

0.000000

0.000000

0.000000

37Ca

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

*A*

0.003032

0.012069

0.000941

0.002732

0.002547

0.003272

0.006508

0.002634

0.002389

0.002166

Apparent Age 

(Ma)

315.93

323.80

326.93

327.48

326.79

323.64

315.66

325.73

330.51

333.34

±

±

±

±

±

±

±

±

±

±

Precision 

(Ma)

1.60

0.23

0.68

0.45

0.27

0.29

1.19

0.26

0.15

0.38

All gas quantities are in moles x 10~' 2 .

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 13D.

Temperature

°C

= 0.009899

850

950 

975 

1025 

1050 

1050

1100 

1150 

1200 

1250 

Total Gas

T65 MUSCOVITE #25RD72 v 4/1 7/98 1

% 39Ar 

of total

3.5

13.9 

2.0 

8.1 

13.9 

10.6

13.9 

13.2 

15.3 

5.7 

100.0

Radiogenic 

Yield (%)

96.

96. 

97. 

98 

99 

98.

97. 

99 

99 

98 

98

.1

.2 

.9 

.5 

.2 

.6

.9 

.1 

.3 

.4 

.3

1.

4. 

0. 

2. 

4. 

3.

4. 

4. 

5. 

1. 

32

39A_ ATR

143256

570677 

642174 

662625 

576665 

469546

562901 

318517 

012588 

863402 

.822351

40Ar*/39ArK

19.

19. 

20. 

20 

20, 

19.

19. 

19 

20 

20 

19

.335

.861 

.071 

.108 

.062 

.850

.317 

.990 

.312 

.502 

.940

1:55:39 14 Sep 1999

Apparent Apparent Apparent Age 

K/Ca K/C1 Ma

Sample wt =

3657 315

4361 323,

* * * * * * 326

* * * * * * 327.

* * * * * * 326. 

4357 323.

4973 315

* * * * * * 325

* * * * * * 330

* * * * * * 333, 

* * * 1886.6 324

.930

.803 

.931 

.476 

.791 

.635

.658 

.725 

.508 

.339 

.980

±

± 

± 

± 

± 

±

± 

±

±

±

Precision 

Ma

1.595

0.228 

0.684 

0.453 

0.272 

0.286

1.188 

0.263 

0.153 

0.382

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10"' 2 .

*** Below detection limit.

59
Figure 13. Age spectrum for T65 muscovite.

400

375

OH

350

325

300

T65 

MUSCOVITE

U

I I I I

0 39ArK RELEASED (%) l\. v x

100

60
Table 14A. K92-7-1 1 A MUSCOVITE #26RD93 v 4/17/98 14:48 :47 14Sepl999

RAW DATA

File# Temperature 4°Ar 39Ar 38Ar

35737 750 528283 18893 181

± 151 12 11

35738 850 1503385 56099 699

± 910 48 17

35739 900 2413496 89612 1164

± 2265 62 4

35740 950 4153606 153924 1925

± 5629 310 22

35741 1000 2538511 94060 1224

± 1058 19 13

35742 1050 1771399 65091 856

± 551 29 12

35743 1100 1997156 72796 955

± 541 38 13

35744 1150 1537148 54721 699

± 1546 105 7

All values are in counts. Measured 40Ar/36Ar = 297.2 ±0.5

37Ar

12

15

21

10

9

9

0

12

0

19

0

4

0

10

0

5

36Ar

119

3

91

8

112

2

113

8

108

8

128

10

118

4

96

7

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1 

Manifold factors: All = 1 Splitl - 3.3 Split2 = 10.89 

EA11 = 2 Esplitl = 6.6 Esplit2 = 21.78 

Sensitivity = 3.604 X 10" 17 moles/count. Reproducibility limit = .25 %. Detection limit =

Table 14B. K92-7-1 1 A MUSCOVITE #26RD93 v 4/17/98 14:48 :47

Trap current Manifold

200

200

200

200

200

200

200

200

40 counts.

14Sepl999

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

CORRECTIONS

Temp 39Ar 37Ar - K-derived -

(°C) decav decav 4°Ar 38Ar 37Ar 39Ar

750 7 20 108 254 0 0

850 20 36 319 753 0 0

900 32 16 510 1203 0 0

950 55 0 876 2066 0 0

1000 34 0 535 1263 0 0

1050 23 0 370 874 0 0

1100 26 0 414 977 0 0

1150 20 0 311 735 0 0

Ca-derivec

38Ar

0

0

0

0

0

0

0

0

36Ar

0

0

0

0

0

0

0

0

Cl-derived initial 

36Ar 38Ar

0 22

0 17

0 21

0 21

0 20

0 24

0 22

0 18

All values are in counts and have been corrected for mass discrimination.

61
Table 14C. K92-7-11A MUSCOVITE #26RD93 v 4/17/98 14:48:47 14 Sep 1999

MOLAR VALUES

Temperature 40Ar* 39ArK 38Arc, 37Ca 36Ari

(°C)

750 38.070880 1.364261 0.000000 0.002267 0.008601

850 108.340970 4.050868 0.000000 0.004117 0.006619

900 173.928057 6.470852 0.000000 0.001810 0.008125

950 299.328795 11.114807 0.000000 0.000000 0.008191

1000 182.937287 6.792001 0.000000 0.000000 0.007808

1050 127.655732 4.700170 0.000631 0.000000 0.009306

1100 143.925143 5.256551 0.000170 0.000000 0.008568

1150 110.775217 3.951401 0.000000 0.000000 0.006940

All gas quantities are in moles x 10"' 2 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 14D. K92-7-1 1 A MUSCOVITE #26RD93 v 4/17/98 14:48:47

Temperature % 39Ar Radiogenic 39ArK 40Ar*/39ArK Apparent Apparent

°C of total Yield (%) K/Ca K/C1

J = .007400 0.5% Sample wt =0.0995 g

750 3.1 93.3 1.364261 26.043 313.0

850 9.3 98.2 4.050868 26.262 511.7 ***

900 14.8 98.6 6.470852 26.508 1859.2 * * *

950 25.4 99.2 11.114807 26.713 *** ***

1000 15.5 98.7 6.792001 26.595 * * *

1050 10.8 97.8 4.700170 26.575 * * * 18035

1100 12.0 98.2 5.256551 26.898 * * * 74801

1150 9.0 98.1 3.951401 27.515 * * * 

Total Gas 100.0 98.4 43.700911 26.681 332.5 10937

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10" 12 .

*** Below detection limit.

Apparent Age

(Ma)

317.93 ±

320.38 ±

323.12 ±

325.41 ±

324.09 ±

323.87 ±

327.48 ±

334.33 ±

14 Sep 1999

Apparent Age

Ma

317.93 ±

320.38 ±

323.12 ±

325.41 ±

324.09 ±

323.87 ±

327.48 ±

334.33 ± 

325.06 ±

Precision

(Ma)

0.58

0.53

0.29

0.44

0.32

0.52

0.19

0.53

Precision

Ma

0.58

0.53

0.29

0.44

0.32

0.52

0.19

0.53

62
Figure 14. Age spectrum for K92-7-11A muscovite.

300

375

«? 350

s-»

S

325

300

K92-7-11A 

MUSCOVITE

I I

0 39ArK RELEASED % 100

63
Table ISA. K92-7-1 IB MUSCOVITE #20RD93 v 4/17/98 14: 59:56 14Sepl999

RAW DATA

File#

35689

35690

35691

35692

35693

35694

Temperature

650

+

750

±

850

±

900

±

950

+

1000

±

40AR

878102

483

1011981

597

930298

305

309702

166

243744

413

236310

295

39Ar

59313

24

56029

42

54137

25

17003

18

11510

24

12198

30

38Ar

1091

10

1020

12

998

7

256

25

103

12

149

5

37Ar

131

5

116

12

89

7

13

5

0

9

21

4

36 Ar

853

1 1

1003

5

1026

3

328

6

158

2

177

6

Trap current

200

200

200

200

200

200

Manifold

BALL

BALL

EALL

BALL

EALL

EALL

All values are in counts. Measured 40Ar/36Ar = 295.7 ± 0.5 

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 - 2.62 200 = 1 

Manifold factors: All - 1 Split 1 =3.3 Split2 = 10.89 

EA11 = 2 Esplitl = 6.6 Esplit2 = 21.78 

Sensitivity = 1.647 X IP' 17 moles/count. Reproducibility limit = .25 %. Detection limit = 40 counts.

Table 15B. K92-7-1 IB MUSCOVITE #20RD93 v 4/17/98 14:59:56 14 Sep 1999

CORRECTIONS

Temp 

(°C)

650

750

850

900

950

1000

39Ar 37Ar 

decay decay

21

20

19

6

4

4

All values are in

218

192

147

22

0

35

counts and have

40Ar

338

319

308

97

65

69

K-derived 

38Ar 37Ar

796

752

727

228

155

164

been corrected for mass

0

0

0

0

0

0

 Ca-derivec

39Ar 38Ar

0

0

0

0

0

0

0

0

0

0

0

0

36Ar

0

0

0

0

0

0

Cl-derived initial

36Ar 38Ar

0

0

0

0

0

0

160

189

193

62

30

33

discrimination.

64
Table 15C. K92-7-1 IB MUSCOVITE #20RD93 v 4/17/98 14:59:56 14 Sep 1999

MOLAR VALUES

Temperature 40Ar* 39ArK 38Arc , 37Ca 35Ari

(°C)

650 63.269274 4.282930 0.033011 0.025266 0.061845

750 72.920618 4.045769 0.033111 0.022301 0.072694

850 67.033693 3.909162 0.033646 0.017091 0.074360

900 22.316326 1.227792 0.006505 0.002598 0.023806

950 17.564356 0.831154 0.000000 0.000000 0.011480

1000 17.028254 0.880810 0.001342 0.004054 0.012839

All gas quantities are in moles x 10~' 2 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 15D. K92-7-1 IB MUSCOVITE #20RD93 v 4/17/98 14:59:56

Temperature % 39Ar Radiogenic 39ArK 40Ar*/39ArK Apparent Apparent

°C of total Yield (%) K/Ca K/C1

J = 0.007396 ± 0.5% Sample wt = 0.0716 g

650 28.2 71.1 4.282930 10.505 88.2 314

750 26.7 70.5 4.045769 12.714 94.3 296

850 25.8 67.2 3.909162 11.527 118.9 281

900 8.1 68.5 1.227792 12.447 245.8 457

950 5.5 80.7 0.831154 17.051 * * * 

1000 5.8 77.7 0.880810 15.025 113.0 1589

Total Gas 100.0 70.7 15.177617 12.135 107.1 369

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10"' 2 .

*** Below detection limit.

Apparent Age

(Ma)

134.99 ±

162.13 ±

147.59 ±

158.86 ±

214.26 ±

190.10 ±

14 Sep 1999

Apparent Age

Ma

134.99 ±

162.13 ±

147.59 ±

158.86 ±

214.26 ± 

190.10 ±

155.05

Precision

(Ma)

0.68

0.35

0.21

1.36

0.78

1.64

Precision

Ma

0.68

0.35

0.21

1.36

0.78 

1.64

65
Figure 15. Age spectrum for K92-7-1 IB muscovite.

300

250

200

CL,

150

100

0

K92-7-11B 

MUSCOVITE

39An, N. RELEASED (%

I I

100

66
Table 16A. K92-7-1 1C MUSCOVITE #24RD93 v 4/17/98 15:09 :06 14Sep 1999

RAW DATA

File# Temperature 40Ar 39Ar 38Ar

35700 750 560443 19613 195

± 349 15 5

35701 850 1482735 54755 725

± 1584 57 4

35702 900 2735934 100967 1293

± 1817 29 11

35703 950 4071214 149856 1925

± 3127 46 8

35704 1000 2317795 85633 1106

± 1003 30 5

35705 1050 1509911 55658 715

± 392 27 6

35706 1100 1837454 67188 873

± 1106 24 9

35707 1150 1660197 59655 760

± 1435 31 7

All values are in counts. Measured 40Ar/36Ar = 297.2 ± 0.5

37Ar

5

5

16

5

7

8

1 1

15

16

5

0

16

0

10

0

5

36Ar

124

6

68

3

82

5

80

7

67

4

72

5

60

8

50

12

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1 

Manifold factors: All = 1 Splitl - 3.3 Split2 = 10.89 

EA11 = 2 Esplitl = 6.6 Esplit2 = 21.78 

Sensitivity = 3.604 X 10" 17 moles/count. Reproducibility limit = .25 %. Detection limit =

Table 16B. K92-7-1 1C MUSCOVITE #24RD93 v 4/17/98 15:09 :06

Trap current Manifold

200

200

200

200

200

200

200

200

40 counts.

14Sep 1999

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

CORRECTIONS

TWnn 39Ar 37Ar K HprivpH - - -

<°C) decav decav 4°Ar 38Ar 37Ar 39Ar

750 7 9 112 263 0 0

850 19 27 312 735 0 0

900 36 12 575 1355 0 0

950 53 19 853 2012 0 0

1000 30 27 487 1150 0 0

1050 20 0 317 747 0 0

1100 24 0 382 902 0 0

1150 21 0 339 801 0 0

Ca-derivec 

38Ar

0

0

0

0

0

0

0

0

36Ar

0

0

0

0

0

0

0

0

Cl-derived initial

36Ar 38Ar

0 23

0 13

0 15

0 15

0 13

0 14

0 1 1

0 9

All values are in counts and have been corrected for mass discrimination.

67
Table 16C. K92-7-11C MUSCOVITE #24RD93 v 4/17/98 15:09:06 14 Sep 1999

MOLAR VALUES

Temperature 40Ar* 39ArK 38Arc , 37Ca 36Ars

(°C)

750 40.388657 1.416264 0.000000 0.001013 0.008970

850 106.853090 3.953792 0.000374 0.003167 0.004948

900 197.164719 7.290739 0.000000 0.001446 0.005931

950 293.391636 10.820999 0.000000 0.002216 0.005782

1000 167.031542 6.183476 0.000000 0.003081 0.004854

1050 108.811556 4.019044 0.000000 0.000000 0.005220

1100 132.416140 4.851569 0.000000 0.000000 0.004371

1150 119.642533 4.307624 0.000000 0.000000 0.003616

All gas quantities are in moles x 10" 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 16D. K92-7-1 1C MUSCOVITE #24RD93 v 4/17/98 15:09:06

Temperature % 39Ar Radiogenic 39ArK 40Ar*/39ArK Apparent Apparent

°C of total Yield (%) K/Ca K/C1

J = 0.007396 ± 0.5% Sample wt = 0.0999 g

750 3.3 93.4 1.416264 26.646 727.0

850 9.2 98.6 3.953792 26.656 649.1 25587

900 17.0 99.1 7.290739 26.803 2622.2 * * *

950 25.3 99.4 10.820999 26.955 2539.5 * * *

1000 14.4 99.1 6.183476 26.781 1043.7 * * *

1050 9.4 98.6 4.019044 26.690 * * *

1100 11.3 99.0 4.851569 27.027 *** ***

1150 10.1 99.1 4.307624 27.527 *** *** 

Total Gas 100.0 98.9 42.843507 26.907 1322.2 2361

NO PLATEAU

Apparent Age

(Ma)

324.51 ±

324.61 ±

326.25 ±

327.95 ±

326.00 ±

325.00 ±

328.75 ±

334.29 ±

14 Sep 1999

Apparent Age

Ma

324.51 ±

324.61 ±

326.25 ±

327.95 ±

326.00 ±

325.00 ±

328.75 ±

334.29 ± 

327.41

Precision

(Ma)

0.95

0.38

0.25

0.28

0.21

0.29

0.42

0.73

Precision

Ma

0.95

0.38

0.25

0.28

0.21

0.29

0.42

0.73

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

68
Figure 16. Age spectrum for K92-7-11C muscovite.

400

375

0>

350

a,

325

300

0

K92-7-11C 

MUSCOVITE

I I I I

39A^ RELEASED (%) 100

69
Table 17A. K92-7-29A MUSCOVITE #123RD93 v 4/17/98 15:31:02 14Sepl999

RAW DATA

File# Temperature 40Ar 39Ar 38Ar 37Ar

35810 750 709858 24938 341 2512

± 492 10 8 6

35811 850 2263564 80856 1035 110

± 2074 96 12 19

35812 900 2101729 74738 979 45

± 2080 76 15 10

35813 950 2413193 85556 1105 65

± 859 9 15 15

35814 1000 2223686 78406 1006 42

± 1019 22 8 7

35815 1050 1260102 43751 580 66

± 1942 22 8 15

35816 1100 732360 25183 325 93

± 1734 38 5 6

All values are in counts. Measured 40Ar/36Ar = 295.7 ± 0.5

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1 

Manifold factors: All = 1 Splitl = 3.3 Split2 = 10.89 

EA11 = 2 Esplitl = 6.6 Esplit2 = 21.78 

Sensitivity = 3.607 X 10' 17 moles/count. Reproducibility limit = .25 %. Detection

Table 17B. K92-7-29A MUSCOVITE #123RD93 v 4/17/98 15:

CORRECTIONS

36Ar

76

10

55

3

45

2

57

3

55

5

58

5

56

5

limit =

31:02

Temp 39Ar 37Ar - K-derived Ca-derivec 

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar

750 10 4856 142 335 050

850 31 213 460 1085 000

900 29 88 425 1003 000

950 33 127 487 1149 000

1000 30 81 446 1053 000

1050 17 128 249 587 000

1100 10 180 143 338 000

2

0

0

0

0

0

0

Trap current Manifold

200

200

200

200

200

200

200

40 counts.

14 Sep 1999

Cl-derived initial 

36Ar 38Ar

0 14

0 10

0 8

0 1 1

0 10

0 1 1

0 1 1

EALL

BALL

EALL

EALL

EALL

EALL

EALL

All values are in counts and have been corrected for mass discrimination.

70
Table 17C. K92-7-29A MUSCOVITE #123RD93 v 4/17/98 15:31:02 14 Sep 1999

MOLAR VALUES

Temperatun 40Ar* 39ArK 38Arc , 37Ca 36Ari

(°C)

750 51.156321 1.800458 0.001501 0.533386 0.005392

850 163.124550 5.838703 0.000000 0.023410 0.003984

900 151.461971 5.396946 0.000000 0.009610 0.003264

950 173.907860 6.178106 0.000000 0.013900 0.004093

1000 160.251147 5.661847 0.000000 0.008898 0.004012

1050 90.810233 3.159299 0.000360 0.014002 0.004190

1100 52.778208 1.818496 0.000000 0.019753 0.004080

All gas quantities are in moles x 10~' 2 .

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

Table 17D. K92-7-29A MUSCOVITE #123RD93 v 4/17/98 15:31:02

Temperature % 39Ar Radiogenic 39ArK 40Ar*/39ArK Apparent Apparent

°C of total Yield (%) K/Ca K/C1

J = 0.007473 ± 0.5% Sample wt = 0.0852 g

750 6.0 96.9 1.800458 27.528 1.8 2903

850 19.6 99.3 5.838703 27.737 129.7

900 18.1 99.4 5.396946 27.886 292.0

950 20.7 99.3 6.178106 27.953 231.1

1000 19.0 99.3 5.661847 28.094 330.9

1050 10.6 98.6 3.159299 28.352 117.3 21217

1100 6.1 97.7 1.818496 28.360 47.9 ***

Total Gas 100.0 99.0 29.853855 27.967 204.2 2420

NO PLATEAU

Apparent Age

(Ma)

337.48 ±

339.82 ±

341.48 ±

342.23 ±

343.80 ±

346.67 ±

346.76 ±

14 Sep 1999

Apparent Age

Ma

±

337.48 ±

339.82 ±

341.48 ±

342.23 ±

343.80 ±

346.67 ±

346.76 ±

342.38

Precision

(Ma)

1.29

0.32

0.33

0.17

0.24

0.62

0.97

Precision

Ma

1.29

0.32

0.33

0.17

0.24

0.62

0.97

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10"' 2 .

*** Below detection limit. ___

71
Figure 17. Age spectrum for K92-7-29A muscovite.

400

375

60

<D

350

325

3000

K92-7-29A 

MUSCOVITE

I I

39ArK RELEASED (%) 100

72
Table 18A. CBR- 10-92 BIOTITE #66RD93 V 4/1 7/98 16:34:09 14Sepl999

RAW DATA

File#

35848

Temperature

1450

±

40Ar

3577800 

1455

39Ar

125698 

232

38Ar

3510 

15

37Ar

52 

12

36Ar Trap current

241 100 

3

Manifold

EALL

All values are in counts. Measured 40Ar/36Ar = 295.7 ± 0.5 

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1 

Manifold factors: All = 1 Splitl = 3.3 Split2 = 10.89 

EA11 = 2 Esplitl =6.6 Esplit2 = 21.78

Sensitivity = 1.647 X 10" 18 moles/count. Reproducibility limit = .25 %. Detection limit = ^

Table 18B. CBR-10-92 BIOTITE #66RD93 v 4/17/98 16:34:09 14

CORRECTIONS

Temp 39Ar 37Ar - K-derived Ca-derivec 

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar

1450 50 105 715 1687 0000

All values are in counts and have been corrected for mass discrimination.

Table 18C. CBR-10-92 BIOTITE #66RD93 v 4/17/98 16:34:09 14

MOLAR VALUES

Temperature 40Ar* 39ArK 38Arc, 37Ca 36An

1450 675.530932 23.781560 0.354746 0.029738 0.045776

10 counts.

Sep 1999

LIC/11VCU ]

36Ar

0

Sep 1999

Apparent Age 

(Ma)

340.06

initial

38Ar

45

Precision 

(Ma)

± 0.16

All gas quantities are in moles x 10~ 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 18D. CBR-10-92 BIOTITE #66RD93 v 4/17/98 16:34:09 14 Sep 1999

MOLAR VALUES

Temperature 

(°C)

750

850

900

950

1000

1050

1100

40 Ar*

51.156321

163.124550

151.461971

173.907860

160.251147

90.810233

52.778208

39 AArK

1.800458

5.838703

5.396946

6.178106

5.661847

3.159299

1.818496

38 A_ Arci

0.001501

0.000000

0.000000

0.000000

0.000000

0.000360

0.000000

37Ca

0.533386

0.023410

0.009610

0.013900

0.008898

0.014002

0.019753

36ATi

0.005392

0.003984

0.003264

0.004093

0.004012

0.004190

0.004080

Apparent Age 

(Ma)

337.48 ±

339.82 ±

341.48 ±

342.23 ±

343.80 ±

346.67 ±

346.76 ±

Precision 

(Ma)

1.29

0.32

0.33

0.17

0.24

0.62

0.97

All gas quantities are in moles x 10~ 12 . 

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0. 

All precision estimates are at the one sigma level of precision. 

No error is calculated for the total gas age.

73
Table 19A. RR89-28 BIOTITE #60RD74 v 4/17/98 12:33:01 14 Sep 1999

RAW DATA

File # Temperature Ar

All

26550

26551

26553

26555

26556

26557

26559

26560

26561

26562

26563

650

±

750

±

950

±

1000

±

1050

±

1100

±

1150

±

1150

±

1200

±

1250

±

1450

±

375960

186

2700909

1561

1765871

404

1604252

1604

4276601

2529

1556946

985

1443367

683

2734542

1260

1220985

398

361642

158

608564

348

values are in counts. Measured 40Ar/36Ar =

Precisions are at the

Trap current factors

1 sigma

: 40 = 3.

Manifold factors: All = 1

EA11 = 2

Sensitivity = 1.344

39Ar

20502

14

112384

103

67446

36

61394

57

166799

138

60909

31

56553

18

106953

68

47531

42

13915

17

24230

31

297.2 ± 0.

38Ar

488

10

2662

9

1423

15

1278

12

3915

16

1310

18

1182

10

2477

7

989

15

294

7

468

16

5

37Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

36Ar Trap current

268

8

309

7

241

10

166

3

253

5

72

7

59

5

113

5

81

6

47

3

53

2

200

200

200

200

200

200

200

200

200

200

200

Manifold

ALL

ALL

SPLIT

SPLIT

ALL

SPLIT

SPLIT

ALL

ALL

ALL

ALL

1

1

1

1

level and are from linear regression statistics.

57 100= 1.4 200

Splitl = 4.2

= 1

Split2= 17.64

.26 Esplitl = 9.49 Esplit2 =

X 10" 17 moles/count. Reproducibility

39.87

limit = .25 %. Detection limit = 40 counts.

74
Table 19B. RR89-28 BIOTITE #60RD74 v 4/17/98 12:33:01 14 Sep 1999

CORRECTIONS

Temp 39Ar 37Ar - K-derived - C

(°C) decay decay 40Ar 38Ar 37Ar 39Ar

650 24 0 117 275 0 0

750 132 0 640 1510 0 0

950 79 0 384 906 0 0

1000 72 0 350 825 0 0

1050 196 0 950 2241 0 0

1100 71 0 347 818 0 0

1150 66 0 322 760 0 0

1150 126 0 609 1437 0 0

1200 56 0 271 639 0 0

1250 16 0 79 187 0 0

1450 28 0 138 326 0 0

a-derivec 

38Ar 36Ar

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

Cl-derived initial

36Ar 38Ar

0

0

0

0

1

0

0

0

0

0

0

50

58

45

31

48

13

1 1

21

15

9

10

All values are in counts and have been corrected for mass discrimination.

Table 19C. RR89-28 BIOTITE #60RD74 v 4/17/98 12:33 :01 14 Sep 1999

MOLAR VALUES

Temperture 4°Ar* 39ArK 38Arcl 37Ca

(°C)

650 5.051331 0.276269 0.003548 0.000000

750 36.291616 1.514389 0.016365 0.000000

950 99.658231 3.817138 0.031941 0.000000

1050 90.537077 3.474629 0.027570 0.000000

1000 57.464751 2.247636 0.023286 0.000000

1100 87.866892 3.447180 0.028730 0.000000

1150 81.457000 3.200634 0.024677 0.000000

1150 36.744054 1.441209 0.014367 0.000000

1200 16.406395 0.640483 0.004957 0.000000

1250 4.859407 0.187510 0.001575 0.000000

1450 8.177242 0.326503 0.002065 0.000000

All gas quantities are in moles x 10~ 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

36 An

0.003627

0.004166

0.013654

0.009403

0.003415

0.004072

0.003362

0.001521

0.001088

0.000640

0.000715

Apparent Age

(Ma)

200.99

312.94

336.36

338.88

337.18

337.46

337.45

337.98

337.13

334.59

328.34

±

±

±

±

±

±

±

±

±

±

±

Precision

(Ma)

1.53

0.28

0.52

0.38

0.22

0.47

0.38

0.22

0.47

0.81

0.41

75
Table 19D. RR89-28 BIQTITE #60RD74 v 4/17/98 12:33:01 14 Sep 1999

Temperature 

°C

% 39Ar Radiogenic 39ArK 

of total Yield (%)

J = 0.008182 ± 0.5% 

650 1.3

750

950

1050

1000

1100

1150

1150

1200

1250

1450

Total Gas

70.24% of gas

7.4

18.6

16.9

10.9

16.8

15.6

7.0

3.1

0.9

1.6

100.0

on plateau in

78.8

96.6

96.0

96.9

98.2

98.6

98.8

98.8

98.0

96.1

97.4

97.4

1000

0.276269

1.514389

3.817138

3.474629

2.247636

3.447180

3.200634

1.441209

0.640483

0.187510

0.326503

20.573580

through 1200 steps

40Ar*/39ArK Apparent Apparent 

K/Ca K/C1

Sample wt =0. 

14.404 ***

23.152

25.051

25.257

25.118

25.140

25.140

25.184

25.114

24.906

24.397

24.839

Plateau Age

***

***

***

***

***

***

***

***

***

***

***

=337.67 ± 1

.1013 g 

188

224

289

305

234

290

314

243

313

288

383

283

.72

Apparent Age Precision 

Ma Ma

200.99

312.94

336.36

338.88

337.18

337.46

337.45

337.98

337.13

334.59

328.34

333.76

±

±

±

±

±

±

±

±

±

±

±

1.53

0.28

0.52

0.38

0.22

0.47

0.38

0.22

0.47

0.81

0.41

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArR gas quantities are in moles x 10" 12 .

*** Below detection limit.

76
Figure 19A. Age spectrum for RR89-28 biotite. 

450

60

o.

OH

400

350

300

250

200

150

0

RR89-28

BIOTITE

PLATEAU AGE = 337.7 ± 1.7 Ma

I I I I

39ArK RELEASED (%) 100

77
Figure 19B. Inverse isotope correlation diagram for RR89-28 biotite. Points C,D,E,F,G,H,I,and J? 

which contain 91.3% of the 39Ar released, were regressed. MSWD = 0.328, SUMS = 1.968, initial 

40Ar/36Ar = 273.84 ± 63.19, and apparent age = 337.7 ± 2.3 Ma.

vo 

o 

o 

o

O ' ^fl

o 

o 

o

o 

o 

o

RR89-28

01 .02 .03

39 40

Ar/ Ar

.04 05 .06

W/O POINTS ABK

78
Table 20A. K92-5-16B BIOTITE #56RD93 v 4/17/98 16:36:50 14 Sep 1999__________ 

___________________________________RAW DATA___________________________ 

File # Temperature 40Ar_____39Ar_____38Ar 37Ar 36Ar Trap current Manifold 

35845 1450 3308942 109416 2534 471 1228 100 EALL 

_____________±______1661_____72______1_2_____14 3___________________ 

All values are in counts. Measured 40Ar/36Ar = 295.7 ± 0.5 

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1 

Manifold factors: All = 1 Splitl = 3.3 Split2 = 10.89

EA11 = 2 Esplitl = 6.6 Esplit2 = 21.78 

Sensitivity = 3.604 X IP' 17 moles/count. Reproducibility limit = .25 %. Detection limit = 40 counts.__________

Table 20B. K92-5-16B BIOTITE #56RD93 v 4/17/98 16:36:50 14 Sep 1999_______

____________________________CORRECTIONS__________________________

Temp 39Ar "Ar - K-derived - - Ca-derivec Cl-derived initial

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1450 43____939 623 1469 0_____1_____0_____0_____0 231

All values are in counts and have been corrected for mass discrimination._______________________

Table 20C. K92-5-16B BIOTITE #56RD93 v 4/17/98 16:36:50 14 Sep 1999

MOLAR VALUES

Temperature

1450

40Ar*

624.774853

39ArK

20.700844

38Arc ,

0.246194

37Ca

0.267452

36Arj Apparent Age 

(Ma)

0.233137 328.67 ±

Precision 

(Ma)

0.196

All gas quantities are in moles x 10 l2 .

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 20D. K92-5-16B BIOTITE #56RD93 v 4/17/98 16:36:50 14 Sep 1999

Temperature 

°C

J = 0.007442

1450

Total Gas

% 39Ar 

of total

± 0.5%

100.0

100.0

Radiogenic j9ArK 

Yield (%)

40Ar*/39ArK Apparent 

K/Ca

Apparent 

K/C1

Apparent Age Precision 

Ma Ma

Sample wt = 0.0502 g

89.0

89.0

20.700844

20.700844

26.853

26.853

40.3

40.2

203

203

328.67

277.68

± 1.53

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0. 

All precision estimates are at the one sigma level. 

No error is calculated for the total gas age. 

39ArK gas quantities are in moles x 10" 12 . 

*** Below detection limit.

79
Table 21A. K92-5-17B BIOTITE #58RD93 v 4/17/98 16:39:32 14Sepl999

RAW DATA

File#

35847

Temperature

850

±

40Ar

4160780 

963

39Ar

121618 

27

38Ar

3205

7

37Ar

2619 

5

36Ar

489 

9

Trap current

100

Manifold

EALL

All values are in counts. Measured 40Ar/36Ar = 295.7 ± 0.5 

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1 

Manifold factors: All = 1 Splitl - 3.3 Split2 = 10.89 

EA11 = 2 Esplitl = 6.6 Esplit2 = 21.78 

Sensitivity = 1.647 X IP' 18 moles/count. Reproducibility limit = .25 %. Detection limit = 40 counts.

Table 21B. K92-5-17B BIOTITE #58RD93 v 4/17/98 16:39:32 14 Sep 1999

CORRECTIONS

Temp 39Ar 37Ar 

(°C) decay decay

850 48 5229

All values are

40Ar

692

K-derived 

38Ar 37Ar

1633 0

39Ar 38Ar 36Ar

502

Cl-derived initial

36Ar 38Ar

0 91

in counts and have been corrected for mass discrimination.

Table 21C. K92-5-17B BIOTITE #58RD93 v 4/17/98 16:39:32 14 Sep 1999

MOLAR VALUES

Temperture 

(°C)

850

40Ar*

785.630995

39ArK

23.008713

38 A,. Arci

0.315863

37Ca

1.488484

36An

0.092379

Apparent Age 

(Ma)

396.10 ±

Precision 

(Ma)

0.256

All gas quantities are in moles x 10" 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 21D. K92-5-17B BIOTITE #58RD93

Temperature % 39Ar 

°C of total

J = 0.007450 ± 0.5% 

850 100.0 

Total Gas 100.0

Radiogenic 39ArK 

Yield (%)

96.5 23.008713 

96.5 23.008713

v 4/17/98 16:39:32 14 Sep 1999

40Ar*/39ArK Apparent Apparent Apparent Age 

K/Ca K/C1 Ma

Sample wt = 0.05 16 g 

32.959 8.0 176 396.10 

32.959 8.0 176 277.68

Precision 

Ma

± 1.80

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0. 

All precision estimates are at the one sigma level. 

No error is calculated for the total gas age. 

39ArK gas quantities are in moles x 10~ 12 . 

*** Below detection limit.

80
Table 22 A. K92-5-17C BIOTITE #60RD93 v 4/17/98 16:46:44 14Sepl999

RAW DATA

File#

35846

Temperature

650

±

40AR

4123907 

2354

39Ar

123975 

59

38Ar

3560 

15

37Ar

1026 

16

36Ar

597 

9

Trap current

100

Manifold

BALL

All values are in counts. Measured 40Ar/36Ar = 295.7 ± 0.5

Precisions are at the 1 sigma level and are from linear regression statistics.

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1

Manifold factors: All = 1 Splitl = 3.3 Split2 = 10.89

EA11 = 2 Esplitl =6.6Esplit2=21.78 

Sensitivity = 3.604E' 17 moles/count. Reproducibility limit = .25 %. Detection limit = 40 counts.________

Table 22B. K92-5-17C BIQTITE #60RD93 v 4/17/98 16:46:44 14 Sep 1999______

____________________________CORRECTIONS_________________________

Temp 39Ar 37Ar - K-derived - Ca-derivec Cl-derived initial

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

650 49 2046 705 1664 0_____2_____0_____1_____0 112

All values are in counts and have been corrected for mass discrimination.______________________

Table 22C. K92-5-17C BIOTITE #60RD93 v 4/17/98 16:46:44 14 Sep 1999

MOLAR VALUES

Temperature 

(°C)

650

40Ar*

778.665047

39ArK

23.455266

38 A r Arci

0.381046

37Ca

0.582748

36Ar;

0.113260

Apparent Age 

(Ma)

382.87 ±

Precision 

(Ma)

0.321

All gas quantities are in moles x 10~ 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 22D.

Temperature 

°C

J = 0.007442 

650 

Total Gas

K92-5-17C BIOTITE

% 39Ar 

of total

± 0.5% 

100.0 

100.0

Radiogenic 

Yield (%)

95.7 

95.7

#60RD93

39ArK

23.455266 

23.455266

v 4/1 7/98 16:46:44

40Ar*/39ArK Apparent 

K/Ca

31.771 

31.771

Sample wt = 

20.93 

20.93

14 Sep

Apparent 

K/C1

0.0505 g 

149 

149

1999

Apparent Age

Ma

382.87 

277.68

Precision

Ma

± 1.76

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0. 

All precision estimates are at the one sigma level. 

No error is calculated for the total gas age. 

39ArK gas quantities are in moles x 10" 12 . 

*** Below detection limit.

81
Table 22A. K92-8-4B BIOTITE #62RD93 v 4/17/98 16:51:03 14 Sep 1999__________ 

___________________________________RAW DATA__________________________ 

File # Temperature 40Ar____39Ar____38Ar 37Ar 36Ar Trap current Manifold 

35819 1450 4061026 128432 1758 395 404 100 EALL 

_____________±_______[69_____107_____H_____3_____9___________________ 

All values are in counts. Measured 40Ar/36Ar = 297.2 ± 0.5 

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 - 2.62 200 = 1 

Manifold factors: All = 1 Splitl = 3.3 Split2 = 10.89 

EA11 = 2 Esplitl =6.6 Esplit2 = 21.78 

Sensitivity = 3.604 X 10' 17 moles/count. Reproducibility limit = .25 %. Detection limit = 40 counts.__________

Table23B. K92-8-4B BIOTITE#62RD93 v4/17/98 16:51:03 14 Sep 1999_______

_____________________________CORRECTIONS___________________________

Temp 39Ar 37Ar - K-derived - - Ca-derivec Cl-derived initial

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1450 50_____767 731 1724 0_____1_____0_____0_____0 76

All values are in counts and have been corrected for mass discrimination._______________________

Table23C. K92-8-4B BIOTITE#62RD93 v4/17/98 16:51:03 14 Sep 1999

MOLAR VALUES

Temperatun 

<°C)

1450

40Ar*

766.785083

39ArK

24.298536

38 Ar ATci

0.021691

37Ca

0.220314

36An

0.076769

Apparent Age 

(Ma)

370.41 ±

Precision 

(Ma)

0.23

All gas quantities are in moles x 10~ 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 23D. K92-8-4B BIOTITE #62RD93

Temperature % 39Ar Radiogenic 39ArK 

°C of total Yield (%)

J = 0.007443 ± 0.5% 

1450 100.0 97 24.298536 

Total Gas 100.0 97 24.298536

v 4/17/98 16:51:03 14 Sep 1999

40Ar*/39ArK Apparent Apparent Apparent Age 

K/Ca K/C1 Ma

Sample wt = 0.0497 g 

30.623 57.35 2711 370.41 

30.623 57.35 2711 277.68

Precision 

Ma

± 1.70

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10" 12 .

*** Below detection limit.____________

82
Table 24A. K92-8-4D BIOTITE #64RD93 v 4/17/98 16:53:34 14 Sep 1999__________

___________________________________RAW DATA__________________________ 

File # Temperature 40Ar_____39Ar_____38Ar 37Ar 36Ar Trap current Manifold 

35821 1450 4165277 131576 1759 266 159 100 BALL 

_____________±______406_____12______8_____9_____4___________________ 

All values are in counts. Measured 40Ar/36Ar = 297.2 ± 0.5 

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 = 2.62 200 = 1 

Manifold factors: All = 1 Splitl = 3.3 Split2 = 10.89 

EA11 = 2 Esplitl - 6.6 Esplit2 =21.78 

Sensitivity = 3.604 X IP' 18 moles/count. Reproducibility limit = .25 %. Detection limit = 40 counts.___________

Table 24B. K92-8-4D BIOTITE #64RD93 v 4/17/98 16:53:34 14 Sep 1999_______

_____________________________CORRECTIONS___________________________

Temp 39Ar 37Ar K-derived Ca-derivec Cl-derived initial

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar 36Ar 38Ar

1450 51_____517 749 1766 0_____1_____0_____0_____0____30

All values are in counts and have been corrected for mass discrimination._______________________

Table 24C. K92-8-4D BIOTITE #64RD93 v 4/17/98 16:53:34 14 Sep 1999

MOLAR VALUES

Temperature

1450

40Ar*

786.469422

39ArK

24.893492

38 A r

ATci

0.005281

37Ca

0.148535

36ATi

0.030177

Apparent Age 

(Ma)

377.23 ±

Precision 

(Ma)

0.12

All gas quantities are in moles x 10" 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

Table 24D. K92-8-4D

Temperature % 39Ar 

°C of total

J = 0.007446 ± 

1450 

Total Gas

0.5% 

100.0 

100.0

BIOTITE #64RD93 v 4/17/98 16:53:34

Radiogenic 39ArK 40Ar*/39ArK Apparent 

Yield (%) K/Ca

Sample wt = 

98.9 24.893492 31.235 87.15 

98.9 24.893492 31.235 87.15

14 Sep 1999

Apparent Apparent Age Precision 

K/C1 Ma Ma

0.0491 g 

11407 377.23 

11407 277.68

± 1.71

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10~ 12 .

*** Below detection limit. _________

83
Table 25A. CBR-10-92 KSPAR #18KD93 v 4/17/98 15:40:55 14 Sep 1999

RAW DATA

File#

35784

35785

35786

35787

35788

35789

35790

35791

35792

35793

35794

35795

35796

35797

35798

35799

35800

All values are

Precisions are

Temperature 40Ar 39Ar

650

±

750

±

800

±

850

±

900

±

950

±

1000

±

1050

±

1100

±

1150

±

1175

±

1200

±

1225

±

1250

±

1275

±

1300

±

1350

±

740692 23559

263 10

1456965 57547

1198 17

1415005 80579

2122 86

1242170 75876

124 27

1197633 67986

1402 168

1005709 54483

240 29

833804 43459

899 51

813346 39902

611 28

900699 39129

162 16

868473 34738

275 60

653760 22172

211 31

721143 18569

553 16

1311526 24800

269 21

2685136 42071

1395 93

4388423 67343

1742 37

1529631 24330

341 34

1662794 27840

151 40

in counts. Measured 40Ar/36Ar = 297.2 ±

at the 1 sigma

Trap current factors: 40 = 5.

Manifold factors: All = 1

Sensitivity =

38Ar

400

11

840

16

1062

6

982

10

905

16

725

7

590

12

562

3

525

10

487

14

324

12

224

4

461

8

849

11

1365

11

484

8

534

10

0.5

37Ar

15

3

0

17

0

7

0

9

9

3

0

19

2

6

21

12

17

5

27

7

7

12

0

20

13

8

0

5

6

7

0

7

13

7

35 Ar Trap current

106

7

145

10

80

6

71

6

69

3

75

6

75

6

57

5

75

7

63

3

54

12

72

6

81

5

130

5

191

7

59

8

68

7

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

Manifold

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

ESPLIT 1

ESPLIT 1

level and are from linear regression statistics.

66 100 = 2.62 200= 1

Split 1 =3.3 Split2 == 10.89

EA11 = 2 Esplitl - 6.6 Esplit2 = 21.78 

3.604 X 10' 17 moles/count. Reproducibility limit = .25 %. Detection limit = 40 counts.

84
Table 25B. CBR-10-92 KSPAR#18KD93 v4/17/98 15:40:55 14 Sep 1999

CORRECTIONS

Temp 39Ar 37Ar - K-derived - Ca-derivec - -

(°C) decay decay 40Ar 38Ar 37Ar 39Ar 38Ar 36Ar

650 9 28 134 316 0 0

750 22 0 327 773 0 0

800 31 0 459 1082 0 0

850 29 0 432 1019 0 0

900 26 17 387 913 0 0

950 21 0 310 731 0 0

1000 17 4 247 583 0 0

1050 15 41 227 536 0 0

1100 15 33 223 525 0 0

1150 13 52 198 466 0 0

1175 9 13 126 298 0 0

1200 7 0 106 249 0 0

1225 10 26 141 333 0 0

1250 16 0 239 565 0 0

1275 26 11 383 904 0 0

1300 9 0 138 327 0 0

1350 11 25 158 374 0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

Cl-derived initial

36Ar 38Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

20

27

15

13

13

14

14

11

14

12

10

14

15

24

36

11

13

All values are in counts and have been corrected for mass discrimination.

Table 25C. CBR-10-92 KSPAR #18KD93 v 4/17/98 15:40::55 14 Sep 1999

MOLAR VALUES

Temperature 40Ar* 39ArK 38Arcl 37Ca

(°C)

650 53.379404 1.701200 0.007555 0.003051

750 104.994430 4.155575 0.007024 0.000000

800 101.960542 5.818754 0.000000 0.000000

850 89.504476 5.479122 0.000000 0.000000

900 86.297495 4.909369 0.000573 0.001924

950 72.469126 3.934299 0.000691 0.000000

1000 60.082780 3.138209 0.001621 0.000488

1050 58.609615 2.881409 0.002767 0.004517

1100 64.906330 2.825533 0.001087 0.003650

1150 62.585269 2.508504 0.002428 0.005690

1175 47.113927 1.601090 0.002719 0.001441

1200 51.972371 1.340863 0.000000 0.000000

1225 94.524647 1.790868 0.010411 0.002830

1250 193.527352 3.038044 0.022430 0.000000

1275 316.289919 4.862944 0.036134 0.001173

1300 363.811238 5.797700 0.040415 0.000000

1350 395.481183 6.634170 0.041630 0.009045

All gas quantities are in moles x 10~ 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

36ATj

0.007678

0.010518

0.005814

0.005167

0.005035

0.005428

0.005419

0.004165

0.005414

0.004530

0.003945

0.005222

0.005837

0.009402

0.013856

0.014062

0.016225

Apparent Age

(Ma)

360.48

299.36

215.41

201.56

215.97

224.64

231.93

246.79

275.43

298.20

345.78

440.94

582.98

685.46

698.24

678.61

649.72

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

Precision

(Ma)

0.92

0.60

0.41

0.26

0.29

0.37

0.57

0.46

0.60

0.31

1.71

1.07

0.57

0.43

0.36

0.93

0.69

85
Table 25D. CBR-10-92 KSPAR #18KD93 v 4/17/98 15:40:55 14 Sep 1999

Temperature % 39Ar 

°C of total

Radiogenic 

Yield (%)

39ArK

J = 0.007362± 0.5%

650

750

800

850

900

950

1000

1050

1100

1150

1175

1200

1225

1250

1275

1300

1350

Total Gas

NO PLATEAU

2.7

6.7

9.3

8.8

7.9

6.3

5.0

4.6

4.5

4.0

2.6

2.1

2.9

4.9

7.8

9.3

10.6

100.0

95.7

97

98.3

98.3

98.3

97.8

97.3

97.9

97.5

97.9

97.5

97

98.2

98.6

98.7

98.9

98.8

98.1

1.701200

4.155575

5.818754

5.479122

4.909369

3.934299

3.138209

2.881409

2.825533

2.508504

1.601090

1.340863

1.790868

3.038044

4.862944

5.797700

6.634170

62.417653

40Ar*/39ArK Apparent 

K/Ca

Sample wt =

30.044

24.518

17.228

16.057

17.275

18.012

18.635

19.913

22.405

24.416

28.698

37.610

51.818

62.787

64.199

62.034

58.890

58.890

289.92

***

***

***

1326.94

0.00

3344.18

331.72

402.56

229.25

577.86

***

329.11

***

2155.96

***

381.41

555.93

Apparent 

K/C1

0.1021 g

545

1432

***

***

20742

13771

4684

2520

6288

2500

1425

***

416

328

326

347

386

3510

Apparent Age Precision 

Ma Ma

360.48

299.36

215.41

201.56

215.97

224.64

231.93

246.79

275.43

298.20

345.78

440.94

582.98

685.46

698.24

678.61

649.72

412.77

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

0.92

0.60

0.41

0.26

0.29

0.37

0.57

0.46

0.60

0.31

1.71

1.07

0.57

0.43

0.36

0.93

0.69

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10" 12 .

*** Below detection limit.

86
Figure 25. Age spectrum for CBR-10-92 Kspar.

800

=

a,

OH

700

600

500

400

300

200

100

0

CBR-10-92 

KSPAR

I I I

39 RELEASED(% 100

87
Table 22A. RRNB-400 Kspar #62 RD74 v.9/21/99 14:34:58 16 Sep 1999

RAW DATA

File # Temperature 40Ar

26565

26566

26567

26568

26569

26570

26571

26572

26573

26574

26575

26576

26577

26578

26579

26580

26581

26582

26583

26584

26585

26586

650

±

750

±

850

±

900

±

950

±

1000

±

1050

±

1100

±

1150

±

1200

±

1250

±

1275

±

1300

±

1325

±

1350

±

1375

±

1400

±

1425

±

1450

±

1550

±

1650

±

1750

±

208197

87

1112543

1081

1502536

1132

4477779

3925

3583746

1110

2784576

2681

2764626

870

2557946

418

1987445

850

2181771

1309

2847551

1773

2376662

1295

2973724

319

2740335

949

2964560

748

3591871

2210

4275428

3551

2050580

339

293849

148

262206

207

1664204

1176

1274581

1005

39Ar

10503

13

70834

48

94452

66

268590

93

207054

124

157074

105

150928

105

135856

61

103146

50

109817

61

137707

64

111184

87

134865

109

120667

75

126150

37

146605

118

169008

94

81151

13

12936

16

12782

8

70818

3

54249

49

All values are in counts. Measured 40Ar/36Ar - 297.2 ± 0.

Precisions are at the

Trap current factors

1 sigma level and are from

:40 = 3

Manifold factors: All = 1

Sensitivity = 1.344 X lO' 17

38Ar

158

8

843

18

902

12

3444

9

2674

14

2051

9

1932

10

1779

6

1342

3

1457

11

1838

14

1494

4

1806

16

1635

4

1695

12

2050

26

2308

9

898

7

135

4

139

9

764

20

590

23

.5

37Ar

3

6

14

10

0

9

9

14

0

6

15

6

32

13

0

3

28

16

0

7

20

9

11

6

0

12

0

13

0

13

9

8

0

11

0

16

0

5

0

10

0

4

2

4

36Ar Trap current

44

6

70

2

33

5

53

5

52

7

50

8

53

7

54

7

54

7

66

9

84

3

67

3

87

9

106

3

111

5

128

7

119

5

55

9

18

2

17

2

56

6

51

4

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

Manifold

BALL

BALL

ESPLIT 1

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

linear regression statistics.

.57 100= 1.4 200= 1

Splitl = 4.2 Split2= 17.64

moles/count. Reproducibility limit = .25

EALL=2. Esplitl = 9.

%. Detection limit = 40

.49 Esplit2

counts.

= 39.87

88
Table 26B. RRNB-400 Kspar #62 RD74 v.9/21/99 14:34:58 16 Sep 1999

CORRECTIONS

Temp 

(°C)

650

750

850

900

950

1000

1050

1100

1150

1200

1250

1275

1300

1325

1350

1375

1400

1425

1450

1550

1650

1750

39Ar 

decay

12

84

111

317

244

185

178

160

122

130

163

131

159

142

149

173

200

96

15

15

84

64

All values are in counts

37Ar 

decay

64

325

0

207

0

368

766

0

679

0

466

253

0

0

0

205

0

0

0

0

0

45

and have

40Ar

60

403

538

1530

1179

895

860

774

587

625

784

633

768

687

718

835

962

462

74

73

403

309

PC-derived

38Ar

141

952

1269

3609

2782

2110

2028

1825

1386

1475

1850

1494

1812

1621

1695

1970

2271

1090

174

172

951

729

been corrected for mass

Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

^

39Ar '

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

"a-derivec 

38Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

 Cl-derived

36Ar 36Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

initial

38Ar

8

13

6

10

10

9

10

10

10

12

16

13

16

20

21

24

22

10

3

3

11

10

discrimination.

89
Table 26C. RRNB-4QQ Kspar #62 RD74 v.9/21/99 14:34:58 16 Sep 1999

MOLAR VALUES

Temperature

650

750

850

900

950

1000

1050

1100

1150

1200

1250

1275

1300

1325

1350

1375

1400

1425

1450

1550

1650

1750

40Ar*

6.322046

33.780559

191.573224

135.963378

108.818315

84.552655

83.947738

77.672561

60.349604

66.250991

86.468832

72.170444

90.301768

83.215146

90.024923

109.075577

129.834312

62.271089

8.923236

7.962126

50.536933

38.705258

1Q AAr

0.319866

2.157173

12.078506

8.179619

6.305611

4.783508

4.596346

4.137345

3.141185

3.344362

4.193711

3.385998

4.107172

3.674802

3.841777

4.464720

5.146973

2.471368

0.393957

0.389251

2.156705

1.652105

38 ArC i

0.00078

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.000280

0.000509

0.000480

0.001177

0.000776

0.003361

0.002020

0.000000

0.000000

0.000000

0.000000

0.000000

37Ca

0.002043

0.010327

0.000000

0.006570

0.000000

0.011695

0.024357

0.000000

0.021573

0.000000

0.014825

0.008040

0.000000

0.000000

0.000000

0.006528

0.000000

0.000000

0.000000

0.000000

0.000000

0.001445

*An

0.001353

0.002149

0.004193

0.001608

0.001604

0.001527

0.001625

0.001654

0.001643

0.002031

0.002547

0.002046

0.002644

0.003244

0.003387

0.003906

0.003644

0.001693

0.000540

0.000504

0.001710

0.001557

Apparent Age 

(Ma)

254.082

213.31

218.45

228.94

236.95

242.10

249.53

255.89

261.02

268.31

278.55

287.33

295.61

302.95

312.75

325.09

335.45

335.18

301.22

273.91

313.06

312.46

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

Precision 

(Ma)

2.22

0.24

0.26

0.21

0.14

0.30

0.18

0.20

0.28

0.33

0.19

0.17

0.25

0.14

0.15

0.25

0.28

0.39

0.70

0.57

0.39

0.34

All gas quantities are in moles x 10" 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

90
Table 26D. RRNB-400 Kspar #62 RD74 v.9/21/99 14:34:58 16 Sep 1999

Temperature % 39Ar Radiogenic 

°C of total Yield (%)

39ArK 40Ar*/39ArK Apparent 

K/Ca

J = 0.008169 ± 0.5

650

750

850

900

950

1000

1050

1100

1150

1200

1250

1275

1300

1325

1350

1375

1400

1425

1450

1550

1650

1750

Total Gas

0.4

2.5

14.2

9.6

7.4

5.6

5.4

4.9

3.7

3.9

4.9

4.0

4.8

4.3

4.5

5.3

6.1

2.9

0.5

0.5

2.5

1.9

100.0

93.7

98.1

99.4

99.7

99.6

99.5

99.4

99.4

99.2

99.1

99.1

99.2

99.1

98.8

98.9

98.9

99.2

99.2

98.2

98.1

99.0

98.8

99.2

0.319866

2.157173

12.078506

8.179619

6.305611

4.783508

4.596346

4.137345

3.141185

3.344362

4.193711

3.385998

4.107172

3.674802

3.841777

4.464720

5.146973

2.471368

0.393957

0.389251

2.156705

1.652105

84.922060

Sample wt =

***

15

15

16

17

17

18

18

19

19

20

21

21

22

23

24

25

24

22

20

23

23

.365

.758

.564

.182

.582

.160

.655

.058

.630

.439

.136

.796

.384

.173

.172

.016

.995

.246

.072

.198

.149

19.605

81.4

108.6

***

647.4

***

212.7

98.1

***

75.7

***

147.1

219.0

***

***

***

355.6

0.0

0.0

0.0

0.0

0.0

594.5

131.8

Apparent 

K/C1

0.2498 g

993

***

***

***

***

***

***

***

***

***

36301

16111

20718

7558

11977

3215

6167

***

***

***

***

***

4852

Apparent Age Precision 

Ma Ma

254.

213.

218.

228,

236,

242.

249.

255.

261.

268.

278.

287.

295.

302.

312.

325.

335.

335.

.08

.31

.45

.94

.95

.10

,53

.89

,02

,31

,55

.33

.61

.95

.75

,09

,45

,18

301.22

273.

313.

,91

,06

312.46

267.,99

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

2.22

0.24

0.26

0.21

0.14

0.30

0.18

0.20

0.28

0.33

0.19

0.17

0.25

0.14

0.15

0.25

0.28

0.39

0.70

0.57

0.39

0.34

Ages calculated assuming an initial ^Ar^Ar = 295. 5± 0.

All precision estimates are

Ages of individual steps do

at the one sigma level.

not include error in the irradiation parameter J.

No error is calculated for the total gas age. 

39ArK gas quantities are in moles x 10" 12 .

*** Below detection limit.

91
Figure 26. Age spectrum for RRNB-400 Kspar.

400

350

300

RRNB-400 

KSPAR

250

2QOA0

I I

39ArK RELEASED (%) 100

92
Table 21 A. RR89-28 KSPAR#61RD74 v4/17/98 11:00:53 14Sepl999

RAW DATA

File#

26598

26599

26600

26601

26602

26603

26604

26605

26606

26607

26608

26609

26610

26611

26612

26613

26614

26615

All values are

Precisions are

Temperature

750

±

800

±

850

±

900

+

950

±

1000

±

1050

+

1100

±

1150

±

1200

±

1250

±

1275

±

1300

±

1325

±

1350

±

1375

±

1400

±

1425

±

40Ar

1956232

458

1557145

1201

1701082

1248

1678586

1011

1726825

816

1729734

1009

1824004

1320

2102774

1791

2677594

640

4409213

3681

1354794

442

3457146

2731

2744431

2657

2802218

1550

2611793

211

3593223

801

3010737

820

843836

313

in counts. Measured 40Ar/36Ar

39Ar

66002

34

111781

79

129013

27

128296

98

131169

97

130130

109

132953

110

147180

88

179341

95

274572

128

77363

12

184150

173

137191

70

127958

114

109645

82

140115

108

115039

71

34376

28

= 297.2 ± 0.

38Ar

889

23

1479

17

1682

7

1674

11

1688

1 1

1680

4

1733

8

1910

15

2345

1 1

3636

7

847

36

2495

10

1862

14

1768

14

1532

11

1960

12

1649

10

384

10

5

"Ar

32

10

40

7

0

9

0

5

14

4

3

9

15

11

8

14

19

7

20

10

23

17

22

16

4

9

0

8

1

10

0

9

0

12

0

2

36Ar

106

4

54

6

43

5

34

4

38

4

41

3

44

3

58

4

89

9

130

4

41

4

104

6

90

7

93

1

79

8

96

7

85

1 1

33

8

Trap current

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

Manifold

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

ESPLIT 1

EALL

EALL

EALL

EALL

EALL

EALL

EALL

at the 1 sigma level and are from linear regression statistics.

Trap current factors: 40 = 3.57

Manifold factors: All = 1

Sensitivity =

EA11 = 2.26

100= 1.4 200= 1

Splitl = 4.2 Split2 = 17.64

Esplitl = 9 .49 Esplit2 =

1.344 X 10~ 17 moles/count. Reproducibility

39.87

limit - .25 %. Detection limit = 40 counts.

93
Table 27B. RR89-28 KSPAR #61RD74 v 4/17/98 11:00:53 14 Sep 1999

CORRECTIONS

Temp 

(°C)

750

800

850

900

950

1000

1050

1100

1150

1200

1250

1275

1300

1325

1350

1375

1400

1425

All values

39Ar 

decay

79

134

155

154

158

156

160

177

216

330

93

222

165

154

132

169

138

41

37Ar 

decay

800

1010

0

0

364

75

371

195

477

513

583

553

93

0

26

0

0

0

40 Ar

376

637

735

731

747

741

757

838

1021

1564

441

1049

781

729

624

798

655

196

K-derived

38Ar

887

1502

1733

1724

1762

1748

1786

1977

2410

3689

1039

2474

1843

1719

1473

1883

1546

462

37Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

£

39Ar

1

1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

^a-derivec 

38Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

 Cl-derived

36Ar 36Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

initial

38Ar

20

10

8

6

7

8

8

1 1

17

24

8

20

17

17

15

18

16

6

are in counts and have been corrected for mass discrimination.

94
Table27C. RR89-28 KSPAR#61RD74 v4/17/98 11:00:53 14 Sep 1999

MOLAR VALUES

Temperatun 40Ar*

750

800

850

900

950

1000

1050

1100

1150

1200

1250

1275

1300

1325

1350

1375

1400

1425

59.407952

47.278010

51.647016

50.963841

52.428575

52.517119

55.380041

63.845049

81.299288

133.879711

172.741797

104.976892

83.336700

85.093557

79.312676

109.117767

91.429445

25.625070

39ArK

2.010037

3.404224

3.929039

3.907203

3.994712

3.963066

4.049041

4.482327

5.461762

8.361989

9.893353

5.608214

4.178103

3.896922

3.339202

4.267162

3.503472

1 .046926

38 Ar Arci

0.000756

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.000000

0.001434

0.001245

0.002172

0.002371

0.003080

0.003782

0.000000

37Ca

0.025375

0.032039

0.000000

0.000000

0.011536

0.002382

0.011759

0.006195

0.015138

0.016251

0.077674

0.017547

0.002948

0.000000

0.000814

0.000000

0.000000

0.000000

36Ari Apparent Age Precision 

(Ma) (Ma)

0.003222

0.001637

0.001327

0.001030

0.001155

0.001265

0.001354

0.001777

0.002711

0.003978

0.005211

0.003177

0.002751

0.002827

0.002403

0.002923

0.002602

0.000997

387.49

193.55

184.16

183.10

184.08

185.67

191.31

198.62

206.75

221.68

240.44

256.58

271.99

295.74

319.78

342.41

348.65

327.92

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

0.26

0.25

0.19

0.16

0.14

0.14

0.16

0.20

0.20

0.18

0.19

0.23

0.32

0.16

0.27

0.20

0.37

0.83

All gas quantities are in moles x 10" 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

95
Table 27D. RR89-28 KSPAR #61RD74 v 4/17/98 11:00:53 14 Sep 1999

Temperature % 39Ar 

°C of total

Radiogenic 

Yield (%)

39ArK

J = 0.008239 ± 0.5%

750

800

850

900

950

1000

1050

1100

1150

1200

1250

1275

1300

1325

1350

1375

1400

1425

Total Gas

NO PLATEAU

2.5

4.3

5.0

4.9

5.0

5.0

5.1

5.7

6.9

10.5

12.5

7.1

5.3

4.9

4.2

5.4

4.4

1.3

100.0

98.4

99.0

99.2

99.4

99.3

99.3

99.3

99.2

99.0

99.1

99.1

99.1

99.0

99.0

99.1

99.2

99.2

98.9

99.1

2.010037

3.404224

3.929039

3.907203

3.994712

3.963066

4.049041

4.482327

5.461762

8.361989

9.893353

5.608214

4.178103

3.896922

3.339202

4.267162

3.503472

1.046926

79.296754

40Ar*/39ArK Apparent Apparent 

K/Ca K/C1

Apparent Age Precision 

Ma Ma

Sample wt = 0.25 19 g

29.082

13.746

13.045

12.966

13.039

13.157

13.579

14.127

14.738

15.870

17.305

18.551

19.751

21.622

23.539

25.369

25.877

24.195

17.501

41.19

55.25

***

***

180.06

865.08

179.06

376.23

187.62

267.57

66.23

166.20

736.96

***

2133.95

***

***

***

275.98

6433

***

***

***

***

***

***

***

***

***

***

9467

8122

4342

3409

3353

2242

***

1897

387.49

193.55

184.16

183.10

184.08

185.67

191.31

198.62

206.75

221.68

240.44

256.58

271.99

295.74

319.78

342.41

348.65

327.92

242.99

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

0.26

0.25

0.19

0.16

0.14

0.14

0.16

0.20

0.20

0.18

0.19

0.23

0.32

0.16

0.27

0.20

0.37

0.83

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39AiK gas quantities are in moles x 10" 12 .

*** Below detection limit.

96
Figure 27. Age spectrum for RR89-28 Kspar.

400

0>=

a.

350

300

250

200

150

1000

RR89-28 

KSPAR

I I I I I I

39ArK RELEASED (%) Is. v '

100

97
Table 28A. K92-5-16A KSPAR #10RD93 v 4/17/98 15:48:59 14Sepl999

RAW DATA

File#

35668

35669

35670

35671

35672

35673

35674

35675

35676

35677

35678

35679

All values

Temperature

850

±

800

±

850

±

900

±

950

±

1000

±

1050

±

1100

±

1150

±

1200

±

1250

±

1300

±

40 Ar

2992365

2629

890161

1551

732720

332

725732

93

659474

453

685822

452

802908

124

1207971

1097

1799485

446

3751527

2600

1956724

2060

4424591

7270

are in counts. Measured 40Ar/36Ar

39Ar

57186

42

46763

116

38973

19

38563

13

34018

18

33056

42

36084

14

47309

18

63976

48

123693

29

57476

34

110457

104

- 297.2 ±

38Ar

980

24

622

14

521

13

509

9

442

4

431

4

494

11

656

20

907

7

1753

14

850

7

1698

15

0.5

"Ar

78

15

85

16

105

5

185

8

149

7

153

3

159

14

166

20

179

7

289

7

101

10

75

16

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 = 2.62 200 - 1 

Manifold factors: All = 1 Splitl = 3.3 Split2 = 10.89 

EA11 = 2 Esplitl =6.6 Esplit2= 21.78 

Sensitivity = 3.604 X 10" 17 moles/count. Reproducibility limit = .25 %. Detection

36Ar

170

6

43

4

40

12

36

9

37

9

40

4

47

3

37

7

63

9

106

8

61

3

160

8

limit

Trap current

200

200

200

200

200

200

200

200

200

200

200

200

= 40 counts.

Manifold

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

ESPLIT 1

BALL

98
Table 28B. K92-5-16AKSPAR#10RD93 v 4/17/98 15:48:59 14 Sep 1999

CORRECTIONS

Temp 39Ar 37Ar - K-derived Ca-(

(°C) decay decay 40Ar 38Ar 37Ar 39Ar

850 20 127 325 768 0 0

800 16 138 266 628 0 0

850 14 171 222 523 0 0

900 13 301 219 518 0 0

950 12 243 194 457 0 0

1000 11 249 188 444 0 0

1050 13 260 205 484 0 0

1100 16 271 269 635 0 0

1150 22 292 364 859 0 0

1200 43 472 704 1660 0 1

1250 20 166 327 772 0 0

1300 38 123 629 1483 0 0

ierivec 

8Ar 36Ar

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

0 0

Cl-derived initial

36Ar 38Ar

0

0

0

0

0

0

0

0

0

0

0

0

32

8

8

7

7

8

9

7

12

20

12

30

All values are in counts and have been corrected for mass discrimination.

Table 28C. K92-5-16A KSPAR #10RD93 v 4/17/98 15:48:59 14 Sep 1999

MOLAR VALUES

Temperatun 40Ar* 39ArK 38Arc, 37Ca

(°C)

850 215.666228 4.129321 0.017828 0.014787

800 64.143610 3.376704 0.000327 0.016168

850 52.798466 2.814183 0.000462 0.019942

900 52.294966 2.784580 0.000000 0.035168

950 47.520919 2.456413 0.000000 0.028415

1000 49.420473 2.386902 0.000000 0.029111

1050 57.858843 2.605595 0.001418 0.030311

1100 87.051175 3.416101 0.002138 0.031587

1150 129.680664 4.619572 0.004542 0.034048

1200 270.359339 8.931658 0.008503 0.055062

1250 465.356356 13.695769 0.022052 0.063904

1300 318.879202 7.975968 0.018012 0.014289

All gas quantities are in moles x 10" 12 .

Ages calculated assuming an initial 40Ar/36Ar = 295. 5± 0.

All precision estimates are at the one sigma level of precision.

Ages of individual steps do not include error in the irradiation parameter J.

36Ar;

0.012287

0.003089

0.002913

0.002594

0.002695

0.002902

0.003398

0.002689

0.004559

0.007700

0.014667

0.011611

Apparent Age

(Ma)

573.75

230.90

227.78

228.35

234.32

249.56

266.37

304.88

332.77

357.06

395.99

457.13

Precision

±

±

±

±

±

±

±

±

±

±

±

±

(Ma)

0.54

0.49

1.03

0.78

0.95

0.41

0.30

0.53

0.47

0.31

0.42

0.71

99
Table 28D. K92-5-16A KSPAR #10RD93 v 4/17/98 15:48:59 14 Sep 1999

Temperature % 39Ar 

°C of total

Radiogenic 

Yield (%)

39 A r ATR

J = 0.007292 ± 0.5%

850

800

850

900

950

1000

1050

1100

1150

1200

1250

1300

Total Gas

NO PLATEAU

7.0

5.7

4.8

4.7

4.1

4.0

4.4

5.8

7.8

15.1

23.1

13.5

100.0

98.3

98.6

98.4

98.5

98.3

98.3

98.3

99.1

99.0

99.2

99.1

98.9

98.8

4.129321

3.376704

2.814183

2.784580

2.456413

2.386902

2.605595

3.416101

4.619572

8.931658

13.695769

7.975968

59.192766

40Ar*/39ArK Apparent 

K/Ca

Sample wt =

51.349

18.726

18.456

18.505

19.021

20.346

21.820

25.250

27.780

30.015

33.662

39.550

30.241

145.21

108.60

73.38

41.17

44.95

42.64

44.70

56.24

70.55

84.35

111.45

290.25

113.68

Apparent 

K/C1

1.0999g

561

25009

14727

***

***

***

4445

3866

2461

2542

1503

1072

3653

Apparent Age Precision 

Ma Ma

573.75

230.90

227.78

228.35

234.32

249.56

266.37

304.88

332.77

357.06

395.99

457.13

359.49

±

±

±

±

±

±

±

±

±

±

±

±

0.54

0.49

1.03

0.78

0.95

0.41

0.30

0.53

0.47

0.31

0.42

0.71

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArK gas quantities are in moles x 10" 12 .

*** Below detection limit.

100
Figure 28. Age spectrum for K92-5-16A Kspar.

800

& o*

700

600

500

400

300

200

100

K92-5-16A 

KSPAR

0

I I I I

39An, RELEASED (%) Iv v y100

101
Table 29 A. K92-5-16B KSPAR #14RD93 v 4/17/98 16: 19:57 14Sepl999

RAW DATA

File#

35758

35759

35760

35761

35762

35763

35764

35765

35766

35767

35768

35769

35770

35771

35772

Temperature 40Ar 39Ar

750

±

800

±

850

±

900

±

950

±

1000

±

1050

±

1100

±

1150

±

1175

±

1200

±

1225

±

1250

±

1275

±

1300

±

1885685 54428

829 11

783513 40370

108 6

698835 36361

456 24

790753 38760

517 80

803437 38780

362 20

906661 42444

192 15

997946 44522

259 19

1239204 49024

1170 18

1771922 62091

418 68

1344016 44418

1173 81

1549964 47334

889 25

2139255 59736

1505 18

3971917 100551

8797 49

1607493 36950

1527 60

3943280 81450

1803 23

All values are in counts. Measured 40Ar/36Ar = 297.2 ±

38Ar

859

12

556

12

509

5

541

11

520

9

583

13

634

24

708

10

906

6

653

10

733

9

951

6

1552

19

596

6

1323

7

0.5

37Ar

43

17

14

10

0

16

28

5

32

7

38

7

57

8

56

5

40

9

38

8

30

7

28

11

20

17

22

10

0

5

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 - 2.62 200 = 1 

Manifold factors: All = 1 Split 1 - 3.3 Split2 = 10.89 

EA11 - 2 Esplitl = 6.6 Esplit2 = 21.78 

Sensitivity = 3.604 X 10" 17 moles/count. Reproducibility limit = .25 %. Detection

36Ar Trap current

282

2

171

4

155

5

139

3

155

8

156

7

173

7

190

8

210

5

198

7

226

4

283

10

418

9

158

5

411

3

limit = 40

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

counts.

Manifold

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

BALL

ESPLIT 1

BALL

102
Table 29B. K92-5-16B KSPAR #14RD93 v 4/17/98 16:19:57 14 Sep 1999

CORRECTIONS

Temp

750 

800 

850 

900 

950 

1000 

1050 

1100 

1150 

1175 

1200 

1225 

1250 

1275 

1300

39Ar 

decay

20 

15 

13 

14 

14 

15 

16 

18 

23 

16 

17 

22 

37 

13 

30

All values are in

37Ar 

decay

74 

24 

0 

48 

55 

65 

99 

97 

70 

66 

53 

49 

36 

39 

0

K derived

40Ar 38Ar 37Ar

310 

230

207 

221 

221 

242 

253 

279 

353 

253 

269 

340 

572 

210 

463

731 0 

542 0 

488 0 

520 0 

521 0 

570 0 

598 0 

658 0 

834 0 

596 0 

635 0 

802 0 

1350 0 

496 0 

1093 0

39Ar 38Ar 36Ar

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0 

0 0

Cl-derived 

36Ar

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0

initial 

38Ar

53 

32 

29 

26 

29 

29 

33 

36 

39 

37 

42 

53 

79 

30 

77

counts and have been corrected for mass discrimination.

Table 29C. K92-5-16B KSPAR #14RD93 v 4/17/98 16:19:57 14 Sep 1999

MOLAR VALUES

Temperature 40Ar*

(°C)

750

800

850

900

950

1000

1050

1100

1150

1175

1200

1225

1250

1275

1300

All gas

135

56.

50.

56.

57.

65.

71.

89.

127

96.

Ill

154

286

382

284

.897828

459070

357083

981580

895810

334737

913662

301685

.694640

858431

.701980

.173022

.254542

.314702

.198228

3

39ArK

.930216

2.915075

2

2

2

3

3

3

4

3

3

4

7

8

5

.625600

.798870

.800287

.064840

.214950

.540002

.483582

.207419

.417979

.313532

.260742

.804903

.881516

38Arc ,

0.013267

0.003450

0.003705

0.003463

0.002148

0.003208

0.005104

0.006345

0.008280

0.006918

0.010253

0.014814

0.020567

0.031339

0.022400

"Ca

0.008422

0.002690

0.000000

0.005515

0.006286

0.007461

0.011241

0.011069

0.007924

0.007570

0.006012

0.005528

0.004044

0.014458

0.000000

36 ATI Apparent Age Precision

0.020417

0.012386

0.011231

0.010099

0.011230

0.011293

0.012562

0.013771

0.015230

0.014358

0.016346

0.020521

0.030286

0.037813

0.029800

(Ma)

392.61

225.70

223.39

239.47

241.76

250.31

261.66

294.24

332.17

347.55

373.55

406.36

446.77

487.34

534.06

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

(Ma)

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

.21

.31

.46

.32

.75

.58

.57

.60

.29

.61

.35

.61

.94

.60

.24

quantities are in moles x 10" 12 .

Ages calculated assuming an initial 40Ar/36Ar - 295.5± 0.

All precision estimates are at the one sigma

Ages of individual steps do not

level of precision.

include error in the irradiation parameter J.

103
Table 29D.

Temperature 

°C

J = 0.007358

750

800

850

900

950

1000

1050

1100

1150

1175

1200

1225

1250

1275

1300

Total Gas

K92-5-16B KSPAR

% 39Ar Radiogenic 

of total Yield (%)

± 0.5%

6.3

4.7

4.2

4.5

4.5

4.9

5.2

5.7

7.2

5.2

5.5

6.9

11.7

14.1

9.4

100.0

95.6

93.5

93.4

94.8

94.3

94.9

94.8

95.4

96.5

95.6

95.7

96.1

96.9

97.1

96.9

95.8

#14RD93

39ArK

3.930216

2.915075

2.625600

2.798870

2.800287

3.064840

3.214950

3.540002

4.483582

3.207419

3.417979

4.313532

7.260742

8.804903

5.881516

62.259513

v 4/1 7/98 16:19:57

40Ar*/39ArK Apparent 

K/Ca

33.043

18.112

17.915

19.293

19.490

20.229

21.214

24.077

27.477

28.875

31.267

34.336

38.192

42.152

46.823

31.294

Sample wt =

242.68

563.50

***

263.91

231.65

213.62

148.72

166.30

294.23

220.32

295.65

405.75

933.63

316.68

***

322.19

14Sep

Apparent 

K/C1

0.1004 g

717

2045

1715

1956

3154

2312

1524

1350

1310

1122

807

705

854

680

635

1214

1999

Apparent Age 

Ma

392.61

225.70

223.39

239.47

241.76

250.31

261.66

294.24

332.17

347.55

373.55

406.36

446.77

487.34

534.06

373.84

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

Precision 

Ma

0.21

0.31

0.46

0.32

0.75

0.58

0.57

0.60

0.29

0.61

0.35

0.61

0.94

0.60

0.24

NO PLATEAU

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39 ArK gas quantities are in moles x 10" 12 .

*** Below detection limit. _ _____

104
Figure 29. Age spectrum for K92-5-16B Kspar.

800

700

600

I

& 50°

I 400

O, 

Q,

300

200

100 0

K92-5-16B 

KSPAR

I I

39ArK RELEASED (%) 100

105
Table 30A. K92-5-17C KSPAR #12RD93 v 4/17/98 16:27:33 14Sepl999

RAW DATA

File # Temperature 40Ar

35710

35711

35712

35713

35714

35715

35716

35717

35718

35719

35720

35721

35722

35723

35724

35725

650

±

750

±

800

±

850

±

900

±

950

±

1000

±

1050

±

1100

±

1150

±

1175

±

1200

±

1225

±

1250

±

1275

±

1300

±

623437

840

1185696

358

1536235

1062

1386789

973

1 160990

648

1165041

470

1294415

163

1380830

461

1546485

1659

1820406

1841

1156975

228

878070

214

877712

401

1112029

2164

1529468

423

974858

396

All values are in counts. Measured 40Ar/36Ar

39Ar

13432

11

78230

33

92703

46

81401

110

65358

19

61877

17

65049

36

65726

11

68494

37

73481

67

43427

10

30174

70

26586

11

29110

64

32390

14

18430

39

= 297.2 ±

38Ar

168

7

1037

16

1211

7

1054

8

861

17

804

13

841

15

879

17

914

4

979

18

596

13

432

12

384

17

437

6

510

5

169

39

0.5

37Ar

12

3

163

21

37

8

30

14

74

8

66

12

81

9

106

11

78

10

55

6

14

12

16

12

0

17

8

8

0

11

0

7

Precisions are at the 1 sigma level and are from linear regression statistics. 

Trap current factors: 40 = 5.66 100 - 2.62 200 = 1 

Manifold factors: All = 1 Split 1 = 3.3 Split2 = 10.89 

EA11 = 2 Esplitl = 6.6 Esplit2 = 21.78 

Sensitivity = 3.604 X 10' 17 moles/count. Reproducibility limit = .25 %. Detection

36Ar

115

5

138

10

98

8

84

2

65

7

74

5

89

4

87

16

106

6

109

4

91

8

81

7

88

8

99

5

114

5

97

3

limit

Trap current

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

200

= 40 counts.

Manifold

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

EALL

106
Table 30B. K92-5-17C KSPAR #12RD93 v 4/17/98 16:27:33 14 Sep 1999

CORRECTIONS

Temp 39Ar

(°C) decay

650

750

800

850

900

950

1000

1050

1100

1150

1175

1200

1225

1250

1275

1300

5

28

33

29

23

22

23

23

24

26

15

11

9

10

12

7

37Ar

decay

20

274

63

50

124

112

137

179

133

94

23

28

0

14

0

0

40Ar

76

445

527

463

372

352

370

374

390

418

247

172

151

166

184

105

K-derived

38Ar

180

1050

1244

1093

877

831

873

882

919

986

583

405

357

391

435

247

37Ar 39Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Ca-derivec

38Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

36Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Cl-derived

36Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

initial

38Ar

22

26

18

16

12

14

17

16

20

20

17

15

17

19

21

18

All values are in counts and have been corrected for mass discrimination.

Table 30C. K92-5-17C KSPAR #12RD93 v 4/17/98 16::27:33 14 Sep 1999

CORRECTIONS

Temp 39Ar

(°C) decay

650

750

800

850

900

950

1000

1050

1100

1150

1175

1200

1225

1250

1275

1300

5

28

33

29

23

22

23

23

24

26

15

11

9

10

12

7

37Ar

decay

20

274

63

50

124

112

137

179

133

94

23

28

0

14

0

0

40Ar

76

445

527

463

372

352

370

374

390

418

247

172

151

166

184

105

K-derived

38Ar

180

1050

1244

1093

877

831

873

882

919

986

583

405

357

391

435

247

37Ar 39Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Ca-derivec

38Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

36Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Cl-derived

36Ar

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

initial

38Ar

22

26

18

16

12

14

17

16

20

20

17

15

17

19

21

18

All values are in counts and have been corrected for mass discrimination.

107
Table 30D. K92-5-17C KSPAR #12RD93 v 4/17/98 16:27:33 14 Sep 1999

Temperature % 39Ar 

°C of total

Radiogenic 

Yield (%)

39 Ar AT|<

J = 0.007356 ±0.5%

650

750

800

850

900

950

1000

1050

1100

1150

1175

1200

1225

1250

1275

1300

Total Gas

NO PLATEAU

1.6

9.2

11.0

9.6

7.7

7.3

7.7

7.8

8.1

8.7

5.1

3.6

3.1

3.4

3.8

2.2

100.0

94.5

96.5

98.1

98.2

98.3

98.1

98.0

98.1

98.0

98.2

97.7

97.3

97.0

97.4

97.8

97.0

97.8

0.969882

5.648896

6.694006

5.877912

4.719418

4.468074

4.697114

4.746036

4.945911

5.306011

3.135811

2.178866

1.919739

2.102004

2.338833

1.330826

61.079339

40Ar*/39ArK Apparent 

K/Ca

Sample wt =

43.777

14.599

16.224

16.692

17.432

18.437

19.453

20.574

22.075

24.284

25.967

28.249

31.964

37.122

46.084

51.230

22.621

220.01

92.99

479.17

532.89

171.07

179.81

155.02

119.40

168.42

255.62

604.04

355.02

***

695.92

***

***

266.93

Apparent 

K/C1

1.1019g

3303

11823

***

***

***

***

***

10107

9985

10938

3333

1679

1434

1070

802

***

4034

Apparent Age Precision 

Ma Ma

503.61

184.03

203.39

208.93

217.66

229.43

241.27

254.24

271.45

296.50

315.35

340.60

380.96

435.54

526.63

576.91

277.68

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

1.32

0.47

0.33

0.16

0.40

0.29

0.23

0.86

0.41

0.34

0.60

0.75

0.93

0.95

0.48

0.57

Ages calculated assuming an initial 40Ar/36Ar = 295.5± 0.

All precision estimates are at the one sigma level.

Ages of individual steps do not include error in the irradiation parameter J.

No error is calculated for the total gas age.

39ArR gas quantities are in moles x 10" 12 .

*** Below detection limit. _____ ____

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REFERENCES

Burton, W.C., Froelich, A.J., Schindler, J.S., and Southworth, S., 1992, Geologic map of 

Loudoun County, Virginia: U.S. Geological. Survey, Open File Report 92-716, 15 

p., 1 plate.

Dalrymple, G.B., Alexander, E.G., Lanphere,M.A., and Kraker, G.P., 1981, Irradiation of 

samples for 40Ar/39Ar dating using the Geological Survey TRIGA reactor: U.S. 

Geol. Survey Professional. Paper 1176, 55p.

Fleck, R.J., Sutler, J.F., and Elliot, D.H., 1977, Interpretation of discordant 40Ar/39Ar age 

spectra of Mesozoic tholeiiles from Antarctica: Geochim. Cosmochim. Acta, v.41, 

p. 15-32.

Haugerud, R.A., and Kunk, M.J., 1988, ArAr*, a computer program for reduction of 40Ar39Ar data: U.S. Geological. Survey, Open File Report. 88-261, 68p.

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Clarke and Loudoun Counties, Virginia, and Jefferson county, West Virginia: U.S. 

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Staudacher, Th., Jessberger, E.K., Dorflinger, D. and Kiko, J., 1978, A refined ultrahighvacuum furnace for rare gas analysis: J.Phys. E. Sci. Instrum. V.I 1, p. 1-11.

110
Steiger, R.H., and Jager, E., 1977, Subcommission on geochronology: Convention on the 

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Letters, v.36, p.359-363.

Ill